feat: audit oauth2 app management (#12275)

* Audit oauth2 app management
* Use 201 for creating secrets

coderd/database/migrations/000197_oauth2_provider_app_audit.down.sql

@@ -0,0 +1,2 @@
+-- It is not possible to drop enum values from enum types, so the UPs on
+-- resource_type have "IF NOT EXISTS".

coderd/database/migrations/000197_oauth2_provider_app_audit.up.sql

@@ -0,0 +1,2 @@
+ALTER TYPE resource_type ADD VALUE IF NOT EXISTS 'oauth2_provider_app';
+ALTER TYPE resource_type ADD VALUE IF NOT EXISTS 'oauth2_provider_app_secret';