Add missing type hints to non-client REST servlets. (#10817)

Including admin, consent, key, synapse, and media. All REST servlets
(the synapse.rest module) now require typed method definitions.

synapse/rest/key/v2/local_key_resource.py

@@ -12,16 +12,21 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-
 import logging
+from typing import TYPE_CHECKING
 
 from canonicaljson import encode_canonical_json
 from signedjson.sign import sign_json
 from unpaddedbase64 import encode_base64
 
 from twisted.web.resource import Resource
+from twisted.web.server import Request
 
 from synapse.http.server import respond_with_json_bytes
+from synapse.types import JsonDict
+
+if TYPE_CHECKING:
+    from synapse.server import HomeServer
 
 logger = logging.getLogger(__name__)
 
@@ -58,18 +63,18 @@ class LocalKey(Resource):
 
     isLeaf = True
 
-    def __init__(self, hs):
+    def __init__(self, hs: "HomeServer"):
         self.config = hs.config
         self.clock = hs.get_clock()
         self.update_response_body(self.clock.time_msec())
         Resource.__init__(self)
 
-    def update_response_body(self, time_now_msec):
+    def update_response_body(self, time_now_msec: int) -> None:
         refresh_interval = self.config.key_refresh_interval
         self.valid_until_ts = int(time_now_msec + refresh_interval)
         self.response_body = encode_canonical_json(self.response_json_object())
 
-    def response_json_object(self):
+    def response_json_object(self) -> JsonDict:
         verify_keys = {}
         for key in self.config.signing_key:
             verify_key_bytes = key.verify_key.encode()
@@ -94,7 +99,7 @@ class LocalKey(Resource):
             json_object = sign_json(json_object, self.config.server.server_name, key)
         return json_object
 
-    def render_GET(self, request):
+    def render_GET(self, request: Request) -> int:
         time_now = self.clock.time_msec()
         # Update the expiry time if less than half the interval remains.
         if time_now + self.config.key_refresh_interval / 2 > self.valid_until_ts: