feat: [AlloyDb] Add new field in GenerateClientCertificate v1 API to allow AlloyDB connectors request client certs with metadata exchange support

AlloyDb/src/V1/Gapic/AlloyDBAdminGapicClient.php

@@ -1869,6 +1869,10 @@ public function failoverInstance($name, array $optionalArgs = [])
      *           default duration.
      *     @type string $publicKey
      *           Optional. The public key from the client.
+     *     @type bool $useMetadataExchange
+     *           Optional. An optional hint to the endpoint to generate a client
+     *           ceritificate that can be used by AlloyDB connectors to exchange additional
+     *           metadata with the server after TLS handshake.
      *     @type RetrySettings|array $retrySettings
      *           Retry settings to use for this call. Can be a {@see RetrySettings} object, or an
      *           associative array of retry settings parameters. See the documentation on
@@ -1897,6 +1901,12 @@ public function generateClientCertificate($parent, array $optionalArgs = [])
             $request->setPublicKey($optionalArgs['publicKey']);
         }
 
+        if (isset($optionalArgs['useMetadataExchange'])) {
+            $request->setUseMetadataExchange(
+                $optionalArgs['useMetadataExchange']
+            );
+        }
+
         $requestParams = new RequestParamsHeaderDescriptor(
             $requestParamHeaders
         );