Adds collapsible sections to API template (#1789)

Author: lcawl

shared/api-ref-ex.asciidoc

@@ -57,7 +57,9 @@ and `manage_follow_index` index privileges...
 ////
 Add a more detailed description the context.
 Link to related APIs if appropriate.
+////
 
+////
 Guidelines for parameter documentation
 ***************************************
 * Use a definition list.
@@ -67,11 +69,8 @@ Guidelines for parameter documentation
 * Include a range of valid values, if applicable.
 * If the parameter requires a specific delimiter for multiple values, say so.
 * If the parameter supports wildcards, ditto.
-* For large or nested objects, consider linking to a separate definition list.
 ***************************************
 ////
-
-
 [[sample-api-path-params]]
 ==== {api-path-parms-title}
 ////
@@ -97,7 +96,14 @@ files to the follower index. The default is `0`, which means waiting on none of
 the shards to be active.
 ////
 
-
+////
+Guidelines for request and response body documentation
+***************************************
+* For large or nested objects, consider linking to a separate definition list
+or using a collapsible section. For example, see the "get node stats" API or the
+"create anomaly detection jobs" API.
+***************************************
+////
 [[sample-api-request-body]]
 ==== {api-request-body-title}
 ////
@@ -110,6 +116,7 @@ the leader index.
 
 `leader_index`::
 (Required, string) The name of the index in the leader cluster to follow.
+
 ////