Docs: Replace [source,json] with [source,js]

The syntax highlighter only supports [source,js].

Also adds a check to the rest test generator that runs during
the build that'll fail the build if it sees `[source,json]`.

buildSrc/src/main/groovy/org/elasticsearch/gradle/doc/RestTestsFromSnippetsTask.groovy

@@ -87,6 +87,10 @@ public class RestTestsFromSnippetsTask extends SnippetsTask {
          * calls buildTest to actually build the test.
          */
         void handleSnippet(Snippet snippet) {
+            if (snippet.language == 'json') {
+                throw new InvalidUserDataException(
+                        "$snippet: Use `js` instead of `json`.")
+            }
             if (snippet.testSetup) {
                 setup(snippet)
                 return

docs/plugins/analysis-icu.asciidoc

@@ -48,7 +48,7 @@ convert `nfc` to `nfd` or `nfkc` to `nfkd` respectively:
 Here are two examples, the default usage and a customised character filter:
 
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -96,7 +96,7 @@ but adds better support for some Asian languages by using a dictionary-based
 approach to identify words in Thai, Lao, Chinese, Japanese, and Korean, and
 using custom rules to break Myanmar and Khmer text into syllables.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -137,7 +137,7 @@ As a demonstration of how the rule files can be used, save the following user fi
 
 Then create an analyzer to use this rule file as follows:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -167,7 +167,7 @@ POST icu_sample/_analyze?analyzer=my_analyzer&text=Elasticsearch. Wow!
 
 The above `analyze` request returns the following:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 # Result
 {
@@ -198,7 +198,7 @@ You should probably prefer the <<analysis-icu-normalization-charfilter,Normaliza
 
 Here are two examples, the default usage and a customised token filter:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -244,7 +244,7 @@ Case folding of Unicode characters based on `UTR#30`, like the
 on steroids. It registers itself as the `icu_folding` token filter and is
 available to all indices:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -278,7 +278,7 @@ to note that both upper and lowercase forms should be specified, and that
 these filtered character are not lowercased which is why we add the
 `lowercase` filter as well:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {
@@ -319,7 +319,7 @@ which is a best-effort attempt at language-neutral sorting.
 Below is an example of how to set up a field for sorting German names in
 ``phonebook'' order:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT /my_index
 {
@@ -452,7 +452,7 @@ rulesets are not yet supported.
 
 For example:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT icu_sample
 {

docs/plugins/analysis-kuromoji.asciidoc

@@ -146,7 +146,7 @@ If both parameters are used, the largest number of both is applied.
 
 Then create an analyzer as follows:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -178,7 +178,7 @@ POST kuromoji_sample/_analyze?analyzer=my_analyzer&text=東京スカイツリー
 
 The above `analyze` request returns the following:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 # Result
 {
@@ -204,7 +204,7 @@ The above `analyze` request returns the following:
 The `kuromoji_baseform` token filter replaces terms with their
 BaseFormAttribute. This acts as a lemmatizer for verbs and adjectives.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -253,7 +253,7 @@ part-of-speech tags. It accepts the following setting:
     An array of part-of-speech tags that should be removed. It defaults to the
     `stoptags.txt` file embedded in the `lucene-analyzer-kuromoji.jar`.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -322,7 +322,7 @@ to `true`. The default when defining a custom `kuromoji_readingform`, however,
 is `false`.  The only reason to use the custom form is if you need the
 katakana reading form:
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -379,7 +379,7 @@ This token filter accepts the following setting:
     is `4`).
 
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -425,7 +425,7 @@ the predefined `_japanese_` stopwords list.  If you want to use a different
 predefined list, then use the
 {ref}/analysis-stop-tokenfilter.html[`stop` token filter] instead.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {
@@ -480,7 +480,7 @@ The above request returns:
 The `kuromoji_number` token filter normalizes Japanese numbers (kansūji)
 to regular Arabic decimal numbers in half-width characters.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT kuromoji_sample
 {

docs/plugins/analysis-phonetic.asciidoc

@@ -50,7 +50,7 @@ The `phonetic` token filter takes the following settings:
     token. Accepts `true` (default) and `false`.  Not supported by
     `beidermorse` encoding.
 
-[source,json]
+[source,js]
 --------------------------------------------------
 PUT phonetic_sample
 {

docs/plugins/lang-javascript.asciidoc

@@ -51,7 +51,7 @@ See <<lang-javascript-file>> for a safer option.
 If you have enabled {ref}/modules-scripting-security.html#enable-dynamic-scripting[inline scripts],
 you can use JavaScript as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 
@@ -94,7 +94,7 @@ See <<lang-javascript-file>> for a safer option.
 If you have enabled {ref}/modules-scripting-security.html#enable-dynamic-scripting[stored scripts],
 you can use JavaScript as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 
@@ -155,7 +155,7 @@ doc["num"].value * factor
 
 then use the script as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 

docs/plugins/lang-python.asciidoc

@@ -50,7 +50,7 @@ See <<lang-python-file>> for a safer option.
 If you have enabled {ref}/modules-scripting-security.html#enable-dynamic-scripting[inline scripts],
 you can use Python as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 
@@ -93,7 +93,7 @@ See <<lang-python-file>> for a safer option.
 If you have enabled {ref}/modules-scripting-security.html#enable-dynamic-scripting[stored scripts],
 you can use Python as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 
@@ -154,7 +154,7 @@ doc["num"].value * factor
 
 then use the script as follows:
 
-[source,json]
+[source,js]
 ----
 DELETE test
 

docs/plugins/repository-azure.asciidoc

@@ -129,7 +129,7 @@ The Azure repository supports following settings:
 
 Some examples, using scripts:
 
-[source,json]
+[source,js]
 ----
 # The simpliest one
 PUT _snapshot/my_backup1

docs/plugins/repository-s3.asciidoc

@@ -137,7 +137,7 @@ use `S3SignerType`, which is Signature Version 2.
 
 The S3 repository is using S3 to store snapshots. The S3 repository can be created using the following command:
 
-[source,json]
+[source,js]
 ----
 PUT _snapshot/my_s3_repository
 {

docs/plugins/store-smb.asciidoc

@@ -68,7 +68,7 @@ Note that setting will be applied for newly created indices.
 
 It can also be set on a per-index basis at index creation time:
 
-[source,json]
+[source,js]
 ----
 PUT my_index
 {

docs/reference/index-modules/allocation/prioritization.asciidoc

@@ -13,7 +13,7 @@ This means that, by default, newer indices will be recovered before older indice
 Use the per-index dynamically updateable `index.priority` setting to customise
 the index prioritization order.  For instance:
 
-[source,json]
+[source,js]
 ------------------------------
 PUT index_1
 
@@ -45,7 +45,7 @@ In the above example:
 This setting accepts an integer, and can be updated on a live index with the
 <<indices-update-settings,update index settings API>>:
 
-[source,json]
+[source,js]
 ------------------------------
 PUT index_4/_settings
 {

docs/reference/migration/migrate_5_0/mapping.asciidoc

@@ -20,7 +20,7 @@ values.  For backwards compatibility purposes, during the 5.x series:
 
 String mappings now have the following default mappings:
 
-[source,json]
+[source,js]
 ---------------
 {
   "type": "text",
@@ -135,7 +135,7 @@ will reject this option.
 Core types no longer support the object notation, which was used to provide
 per document boosts as follows:
 
-[source,json]
+[source,js]
 ---------------
 {
   "value": "field_value",

docs/reference/modules/scripting/security.asciidoc

@@ -165,7 +165,7 @@ https://github.com/elastic/elasticsearch/blob/{branch}/core/src/main/java/org/el
 In a script, attempting to load a class that does not appear in the whitelist
 _may_ result in a `ClassNotFoundException`, for instance this script:
 
-[source,json]
+[source,js]
 ------------------------------
 GET _search
 {
@@ -179,7 +179,7 @@ GET _search
 
 will return the following exception:
 
-[source,json]
+[source,js]
 ------------------------------
 {
   "reason": {
@@ -207,7 +207,7 @@ use(groovy.time.TimeCategory); new Date(123456789).format('HH')
 
 Returns the following exception:
 
-[source,json]
+[source,js]
 ------------------------------
 {
   "reason": {