Moto-1781: Create initial stub of rotate_secret and tests.

moto/secretsmanager/models.py

@@ -36,6 +36,7 @@ class SecretsManagerBackend(BaseBackend):
         self.rotation_enabled = False
         self.rotation_lambda_arn = ''
         self.auto_rotate_after_days = 0
+        self.version_id = ''
 
     def reset(self):
         region_name = self.region
@@ -105,6 +106,20 @@ class SecretsManagerBackend(BaseBackend):
 
         return response
 
+    def rotate_secret(self, secret_id, client_request_token=None,
+                      rotation_lambda_arn=None, rotation_rules=None):
+
+        if not self._is_valid_identifier(secret_id):
+            raise ResourceNotFoundException
+
+        response = json.dumps({
+            "ARN": secret_arn(self.region, self.secret_id),
+            "Name": self.name,
+            "VersionId": self.version_id
+        })
+
+        return response
+
     def get_random_password(self, password_length,
                             exclude_characters, exclude_numbers,
                             exclude_punctuation, exclude_uppercase,