New API test - "Get Designate Limits"

Test scenario:
  Initiate API query to retrieve Designate Limits.
  Ensure that all expected fields presents in received data.

Change-Id: Ib76f30671b5695f73ccd6fe6b7eaa8932b126411
diff --git a/designate_tempest_plugin/clients.py b/designate_tempest_plugin/clients.py
index 43ec5a7..6fbfc05 100644
--- a/designate_tempest_plugin/clients.py
+++ b/designate_tempest_plugin/clients.py
@@ -49,6 +49,8 @@
     import TsigkeyClient
 from designate_tempest_plugin.services.dns.v2.json.service_client \
     import SevriceClient
+from designate_tempest_plugin.services.dns.v2.json.designate_limit_client \
+    import DesignateLimitClient
 
 CONF = config.CONF
 
@@ -96,6 +98,7 @@
         self.transfer_accept_client = TransferAcceptClient(**params)
         self.tsigkey_client = TsigkeyClient(**params)
         self.service_client = SevriceClient(**params)
+        self.designate_limit_client = DesignateLimitClient(**params)
 
         self.query_client = QueryClient(
             nameservers=CONF.dns.nameservers,
diff --git a/designate_tempest_plugin/services/dns/v2/json/designate_limit_client.py b/designate_tempest_plugin/services/dns/v2/json/designate_limit_client.py
new file mode 100644
index 0000000..a4e3aef
--- /dev/null
+++ b/designate_tempest_plugin/services/dns/v2/json/designate_limit_client.py
@@ -0,0 +1,27 @@
+# Copyright 2021 Red Hat.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+from designate_tempest_plugin.services.dns.v2.json import base
+
+
+class DesignateLimitClient(base.DnsClientV2Base):
+
+    @base.handle_errors
+    def list_designate_limits(self, headers=None):
+        """Show the limits for Designate fields
+
+        :param headers: (dict): The headers to use for the request.
+        :return: Dictionary of limits
+        """
+        return self._list_request(
+            'limits', headers=headers)[1]
diff --git a/designate_tempest_plugin/tests/api/v2/test_designate_limits.py b/designate_tempest_plugin/tests/api/v2/test_designate_limits.py
new file mode 100644
index 0000000..a2c92dc
--- /dev/null
+++ b/designate_tempest_plugin/tests/api/v2/test_designate_limits.py
@@ -0,0 +1,52 @@
+# Copyright 2021 Red Hat.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+from oslo_log import log as logging
+from tempest.lib import decorators
+
+from designate_tempest_plugin.tests import base
+
+LOG = logging.getLogger(__name__)
+
+
+class DesignateLimit(base.BaseDnsV2Test):
+    credentials = ['admin']
+
+    @classmethod
+    def setup_credentials(cls):
+        # Do not create network resources for these test.
+        cls.set_network_resources()
+        super(DesignateLimit, cls).setup_credentials()
+
+    @classmethod
+    def setup_clients(cls):
+        super(DesignateLimit, cls).setup_clients()
+
+        cls.admin_client = cls.os_admin.designate_limit_client
+
+    @decorators.idempotent_id('828572be-8662-11eb-8ff2-74e5f9e2a801')
+    def test_list_designate_limits(self):
+        expected_default_limits_fields = [
+            "max_page_limit", "max_recordset_name_length",
+            "max_recordset_records", "max_zone_name_length",
+            "max_zone_records", "max_zone_recordsets",
+            "max_zones", "min_ttl"].sort()
+        project_limits = self.admin_client.list_designate_limits()
+        LOG.info(
+            'Retrieved designate limits are: {} '.format(project_limits))
+        self.assertEqual(
+            expected_default_limits_fields,
+            list(project_limits.keys()).sort(),
+            'Retrieved fields: {} are not as expected: {} '.format(
+                list(project_limits.keys()).sort(),
+                expected_default_limits_fields))