feat: Update cloudbuild proto with the service_account for BYOSA Trig…

…gers. (#274)

* feat: Update cloudbuild proto with the service_account for BYOSA Triggers.

Committer: @emoryruscus
PiperOrigin-RevId: 392957767

Source-Link: googleapis/googleapis@5572865

Source-Link: googleapis/googleapis-gen@bc40f42

* 🦉 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>

protos/google/devtools/cloudbuild/v1/cloudbuild.proto

@@ -1377,6 +1377,15 @@ message BuildTrigger {
 
   // Optional. A Common Expression Language string.
   string filter = 30 [(google.api.field_behavior) = OPTIONAL];
+
+  // The service account used for all user-controlled operations including
+  // UpdateBuildTrigger, RunBuildTrigger, CreateBuild, and CancelBuild.
+  // If no service account is set, then the standard Cloud Build service account
+  // ([PROJECT_NUM]@system.gserviceaccount.com) will be used instead.
+  // Format: `projects/{PROJECT_ID}/serviceAccounts/{ACCOUNT_ID_OR_EMAIL}`
+  string service_account = 33 [(google.api.resource_reference) = {
+    type: "iam.googleapis.com/ServiceAccount"
+  }];
 }
 
 // GitHubEventsConfig describes the configuration of a trigger that creates a