docs: [essentialcontacts] Marks the google.cloud.essentialcontacts.v1.Contact.validation_state field as output_only

packages/google-cloud-essentialcontacts/README.md

@@ -44,7 +44,7 @@ Google APIs Client Libraries, in [Client Libraries Explained][explained].
 1.  [Select or create a Cloud Platform project][projects].
 1.  [Enable billing for your project][billing].
 1.  [Enable the Essential Contacts API API][enable_api].
-1.  [Set up authentication with a service account][auth] so you can access the
+1.  [Set up authentication][auth] so you can access the
     API from your local workstation.
 
 ### Installing the client library
@@ -165,4 +165,4 @@ See [LICENSE](https://github.com/googleapis/google-cloud-node/blob/main/LICENSE)
 [projects]: https://console.cloud.google.com/project
 [billing]: https://support.google.com/cloud/answer/6293499#enable-billing
 [enable_api]: https://console.cloud.google.com/flows/enableapi?apiid=essentialcontacts.googleapis.com
-[auth]: https://cloud.google.com/docs/authentication/getting-started
+[auth]: https://cloud.google.com/docs/authentication/external/set-up-adc-local

packages/google-cloud-essentialcontacts/protos/google/cloud/essentialcontacts/v1/service.proto

@@ -163,9 +163,10 @@ message Contact {
   // for a list of supported languages.
   string language_tag = 4 [(google.api.field_behavior) = REQUIRED];
 
-  // The validity of the contact. A contact is considered valid if it is the
-  // correct recipient for notifications for a particular resource.
-  ValidationState validation_state = 8;
+  // Output only. The validity of the contact. A contact is considered valid if
+  // it is the correct recipient for notifications for a particular resource.
+  ValidationState validation_state = 8
+      [(google.api.field_behavior) = OUTPUT_ONLY];
 
   // The last time the validation_state was updated, either manually or
   // automatically. A contact is considered stale if its validation state was