Extend documentation

Author: gmarouli

server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamFailureStore.java

@@ -251,6 +251,10 @@ public Builder enabled(Boolean enabled) {
             return this;
         }
 
+        /**
+         * Composes the provided enabled value with the current one. Because enabled is a resettable boolean, if it is defined
+         * it will overwrite the current value.
+         */
         public Builder enabled(ResettableValue<Boolean> enabled) {
             if (enabled.isDefined()) {
                 this.enabled = enabled.get();
@@ -263,6 +267,11 @@ public Builder lifecycle(DataStreamLifecycle lifecycle) {
             return this;
         }
 
+        /**
+         * Composes the provided lifecycle value with the current one. Because lifecycle is a resettable template that can be merged,
+         * if it is defined it will delegate to {@link DataStreamLifecycle.Builder#composeTemplate(DataStreamLifecycle.Template)} to
+         * correctly compose the contents.
+         */
         public Builder lifecycle(ResettableValue<DataStreamLifecycle.Template> lifecycle) {
             if (lifecycle.shouldReset()) {
                 this.lifecycleBuilder = null;
@@ -277,6 +286,9 @@ public Builder lifecycle(ResettableValue<DataStreamLifecycle.Template> lifecycle
 
         }
 
+        /**
+         * Composes the provided failure store template with this builder.
+         */
         public Builder composeTemplate(DataStreamFailureStore.Template failureStore) {
             this.enabled(failureStore.enabled());
             this.lifecycle(failureStore.lifecycle());

server/src/main/java/org/elasticsearch/cluster/metadata/DataStreamOptions.java

@@ -182,15 +182,15 @@ public Builder(DataStreamOptions options) {
         }
 
         /**
-         * Updates this builder with the values of the provided template. This is not a replacement necessarily, the
+         * Composes this builder with the values of the provided template. This is not a replacement necessarily, the
          * inner values will be merged.
          */
         public Builder composeTemplate(DataStreamOptions.Template options) {
             return failureStore(options.failureStore());
         }
 
         /**
-         * Updates the current failure store configuration with the provided value. This is not a replacement necessarily, if both
+         * Composes the current failure store configuration with the provided value. This is not a replacement necessarily, if both
          * instance contain data the configurations are merged.
          */
         public Builder failureStore(ResettableValue<DataStreamFailureStore.Template> newFailureStore) {