Add missing type hints to handlers and fix a Spam Checker type hint. (#9896)

The user_may_create_room_alias method on spam checkers
declared the room_alias parameter as a str when in reality it is
passed a RoomAlias object.

synapse/handlers/identity.py

@@ -17,7 +17,7 @@
 """Utilities for interacting with Identity Servers"""
 import logging
 import urllib.parse
-from typing import Awaitable, Callable, Dict, List, Optional, Tuple
+from typing import TYPE_CHECKING, Awaitable, Callable, Dict, List, Optional, Tuple
 
 from synapse.api.errors import (
     CodeMessageException,
@@ -41,13 +41,16 @@ from synapse.util.stringutils import (
 
 from ._base import BaseHandler
 
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
+
 logger = logging.getLogger(__name__)
 
 id_server_scheme = "https://"
 
 
 class IdentityHandler(BaseHandler):
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         super().__init__(hs)
 
         # An HTTP client for contacting trusted URLs.
@@ -80,7 +83,7 @@ class IdentityHandler(BaseHandler):
         request: SynapseRequest,
         medium: str,
         address: str,
-    ):
+    ) -> None:
         """Used to ratelimit requests to `/requestToken` by IP and address.
 
         Args: