Add index_expression_selectors to the search capabilities, rename rollover's to match

Author: jbaiera

modules/data-streams/src/yamlRestTest/resources/rest-api-spec/test/data_stream/210_rollover_failure_store.yml

@@ -9,7 +9,7 @@ setup:
           capabilities: [ 'data_stream_options.failure_store' ]
         - method: POST
           path: /{index}/_rollover
-          capabilities: [ 'index-expression-selectors' ]
+          capabilities: [ 'index_expression_selectors' ]
 
   - do:
       allowed_warnings:
@@ -313,7 +313,7 @@ teardown:
       capabilities:
         - method: POST
           path: /{index}/_rollover
-          capabilities: [index-expression-selectors]
+          capabilities: [index_expression_selectors]
 
   # Initialize failure store
   - do:

server/src/main/java/org/elasticsearch/rest/action/admin/indices/RestRolloverIndexAction.java

@@ -44,7 +44,7 @@ public String getName() {
     @Override
     public Set<String> supportedCapabilities() {
         if (DataStream.isFailureStoreFeatureFlagEnabled()) {
-            return Set.of("return-404-on-missing-target", "index-expression-selectors");
+            return Set.of("return-404-on-missing-target", "index_expression_selectors");
         } else {
             return Set.of("return-404-on-missing-target");
         }

server/src/main/java/org/elasticsearch/rest/action/search/SearchCapabilities.java

@@ -46,6 +46,8 @@ private SearchCapabilities() {}
 
     private static final String HIGHLIGHT_MAX_ANALYZED_OFFSET_DEFAULT = "highlight_max_analyzed_offset_default";
 
+    private static final String INDEX_SELECTOR_SYNTAX = "index_expression_selectors";
+
     public static final Set<String> CAPABILITIES;
     static {
         HashSet<String> capabilities = new HashSet<>();
@@ -63,6 +65,7 @@ private SearchCapabilities() {}
         capabilities.add(K_DEFAULT_TO_SIZE);
         capabilities.add(KQL_QUERY_SUPPORTED);
         capabilities.add(HIGHLIGHT_MAX_ANALYZED_OFFSET_DEFAULT);
+        capabilities.add(INDEX_SELECTOR_SYNTAX);
         CAPABILITIES = Set.copyOf(capabilities);
     }
 }