feat: expose Locations service to get/list avaliable locations of D…

…ialogflow products; fixed some API annotations (#860)

* feat: expose `Locations` service to get/list avaliable locations of Dialogflow products; fixed some API annotations

PiperOrigin-RevId: 389905442

Source-Link: googleapis/googleapis@4c984f3

Source-Link: googleapis/googleapis-gen@ea3337a

* 🦉 Updates from OwlBot

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

packages/google-cloud-dialogflow/protos/google/cloud/dialogflow/v2/intent.proto

@@ -873,12 +873,13 @@ message Intent {
   // copied from the messages in PLATFORM_UNSPECIFIED (i.e. default platform).
   repeated Message.Platform default_response_platforms = 15 [(google.api.field_behavior) = OPTIONAL];
 
+  // Output only.
   // Read-only. The unique identifier of the root intent in the chain of
   // followup intents. It identifies the correct followup intents chain for
   // this intent. We populate this field only in the output.
   //
   // Format: `projects/<Project ID>/agent/intents/<Intent ID>`.
-  string root_followup_intent_name = 16;
+  string root_followup_intent_name = 16 [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // Read-only after creation. The unique identifier of the parent intent in the
   // chain of followup intents. You can set this field when creating an intent,
@@ -890,9 +891,9 @@ message Intent {
   // Format: `projects/<Project ID>/agent/intents/<Intent ID>`.
   string parent_followup_intent_name = 17;
 
-  // Read-only. Information about all followup intents that have this intent as
+  // Output only. Read-only. Information about all followup intents that have this intent as
   // a direct or indirect parent. We populate this field only in the output.
-  repeated FollowupIntentInfo followup_intent_info = 18;
+  repeated FollowupIntentInfo followup_intent_info = 18 [(google.api.field_behavior) = OUTPUT_ONLY];
 }
 
 // The request message for [Intents.ListIntents][google.cloud.dialogflow.v2.Intents.ListIntents].