refactor: Clean up args for fetch_initial_state_data.

We now require explicit keywords for all arguments
to fetch_initial_state_data except user_profile.

We provide reasonable defaults to keep the test
code concise.

zerver/lib/events.py

@@ -83,11 +83,12 @@ def always_want(msg_type: str) -> bool:
 
 def fetch_initial_state_data(
     user_profile: Optional[UserProfile],
-    event_types: Optional[Iterable[str]],
-    queue_id: Optional[str],
-    client_gravatar: bool,
-    user_avatar_url_field_optional: bool,
-    realm: Realm,
+    *,
+    realm: Optional[Realm] = None,
+    event_types: Optional[Iterable[str]] = None,
+    queue_id: Optional[str] = "",
+    client_gravatar: bool = False,
+    user_avatar_url_field_optional: bool = False,
     slim_presence: bool = False,
     include_subscribers: bool = True,
     include_streams: bool = True,
@@ -103,6 +104,10 @@ def fetch_initial_state_data(
     corresponding events for changes in the data structures and new
     code to apply_events (and add a test in test_events.py).
     """
+    if realm is None:
+        assert user_profile is not None
+        realm = user_profile.realm
+
     state: Dict[str, Any] = {'queue_id': queue_id}
 
     if event_types is None:
@@ -965,11 +970,10 @@ def do_events_register(
 
     ret = fetch_initial_state_data(
         user_profile,
-        event_types_set,
-        queue_id,
+        event_types=event_types_set,
+        queue_id=queue_id,
         client_gravatar=client_gravatar,
         user_avatar_url_field_optional=user_avatar_url_field_optional,
-        realm=user_profile.realm,
         slim_presence=slim_presence,
         include_subscribers=include_subscribers,
         include_streams=include_streams,