doc(changelog): Finish the documentation for pipeline config bulk sav…

…e functionality

The documentation for front50 already existed. Adds some sections for the gate and orca changes which make the functionality feature complete.

See relevant PRs
spinnaker/front50#1483, spinnaker/orca#4773, and spinnaker/gate#1823

content/en/docs/releases/next-release-preview/index.md

@@ -12,8 +12,35 @@ changelog.
 ## Coming Soon in Release 1.36
 
 ### Enhanced pipeline batch update feature
+#### Gate
+Adds a new enpdoint, POST /pipelines/bulksave, which can take a list of pipeline configurations to save. The endpoint will return a response that indicates how many of the saves were successful, how many failed, and what the failures are. The structure is
 
-Batch update operation is now atomic. Deserialization issues are addressed. 
+```
+[
+   "successful_pipelines_count"  : <int>,
+   "successful_pipelines"        : <List<String>>,
+   "failed_pipelines_count"      : <int>,
+   "failed_pipelines"            : <List<Map<String, Object>>>
+]
+```
+
+There are a few config knobs which control some bulk save functionality. The gate endpoint invokes an orca asynchronous process to manage saving the pipelines and polls until the orca operations are complete.
+
+```yaml
+controller:
+  pipeline:
+    bulksave:
+      # the max number of times gate will poll orca to check for task status
+      max-polls-for-task-completion: <int>
+      # the interval at which gate will poll orca.
+      taskCompletionCheckIntervalMs: <int>
+```
+
+#### Orca
+Updates Orca's SavePipelineTask to support bulk saves using the updated functionality in the front50 bulk save endpoint.
+
+#### Front50
+Batch update operation in front50 is now atomic. Deserialization issues are addressed.
 
 Configurable controls are added to decide whether cache should be refreshed while checking for duplicate pipelines:
 ```yaml