feat: [iap] Adding programmatic_clients attribute to UpdateIapSettings API request (#4668)

* feat: Adding programmatic_clients attribute to UpdateIapSettings API request

PiperOrigin-RevId: 565783416

Source-Link: googleapis/googleapis@54e08f2

Source-Link: googleapis/googleapis-gen@b86e540
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packages/google-cloud-iap/protos/google/cloud/iap/v1/service.proto

@@ -444,6 +444,9 @@ message OAuthSettings {
   // Note: IAP does not verify that the id token's hd claim matches this value
   // since access behavior is managed by IAM policies.
   google.protobuf.StringValue login_hint = 2;
+
+  // List of Oauth client IDs allowed to programmatically authenticate with IAP.
+  repeated string programmatic_clients = 5;
 }
 
 // Configuration for IAP reauthentication policies.