openapi: Add tests for checking presence of various attributes.

The swagger validator is a basic tool to check whether our
openapi specification file follows the basic syntax. But to ensure
that our zulip.yaml file is not only syntactically compatible but
also describes our API well, we need to add custom tests. This
commit currently checks whether each endpoint has an `operationId`
and a valid tag. It also makes it easier to check for custom rules
in the future.

zerver/tests/test_openapi.py

@@ -15,7 +15,8 @@ from zerver.lib.test_classes import ZulipTestCase
 from zerver.openapi.openapi import (
     get_openapi_fixture, get_openapi_parameters,
     validate_against_openapi_schema, to_python_type,
-    SchemaError, openapi_spec, get_openapi_paths
+    SchemaError, openapi_spec, get_openapi_paths,
+    OpenAPISpec, OPENAPI_SPEC_PATH
 )
 from zerver.lib.request import arguments_map
 
@@ -965,3 +966,20 @@ class TestCurlExampleGeneration(ZulipTestCase):
             '```'
         ]
         self.assertEqual(generated_curl_example, expected_curl_example)
+
+class OpenAPIAttributesTest(ZulipTestCase):
+    def test_attributes(self) -> None:
+        EXCLUDE = ["/real-time"]
+        VALID_TAGS = ["users", "server_and_organizations", "authentication",
+                      "real_time_events", "streams", "messages", "users",
+                      "webhooks"]
+        openapi_spec = OpenAPISpec(OPENAPI_SPEC_PATH).spec()["paths"]
+        for path in openapi_spec:
+            if path in EXCLUDE:
+                continue
+            for method in openapi_spec[path]:
+                # Check if every file has an operationId
+                assert("operationId" in openapi_spec[path][method])
+                assert("tags" in openapi_spec[path][method])
+                tag = openapi_spec[path][method]["tags"][0]
+                assert(tag in VALID_TAGS)