The operation on the changed resource in change_event resource.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v25/enums/resource_change_operation.proto)

| Enums ||
|---|---|
| ## `CREATE` | The resource was created. |
| ## `REMOVE` | The resource was removed. |
| ## `UNKNOWN` | Used for return value only. Represents an unclassified operation unknown in this version. |
| ## `UNSPECIFIED` | No value has been specified. |
| ## `UPDATE` | The resource was modified. |