Parse gateway URL as an actual URL using yarl

Discord has changed the URL format to make it infeasible to edit it
using basic string interpolation.

discord/gateway.py

@@ -35,6 +35,7 @@ import zlib
 from typing import Any, Callable, Coroutine, Dict, List, TYPE_CHECKING, NamedTuple, Optional, TypeVar
 
 import aiohttp
+import yarl
 
 from . import utils
 from .activity import BaseActivity, Spotify
@@ -286,14 +287,14 @@ class DiscordWebSocket:
         _initial_identify: bool
         shard_id: Optional[int]
         shard_count: Optional[int]
-        gateway: str
+        gateway: yarl.URL
         _max_heartbeat_timeout: float
         _user_agent: str
         _super_properties: Dict[str, Any]
         _zlib_enabled: bool
 
     # fmt: off
-    DEFAULT_GATEWAY    = 'wss://gateway.discord.gg/'
+    DEFAULT_GATEWAY    = yarl.URL('wss://gateway.discord.gg/')
     DISPATCH           = 0
     HEARTBEAT          = 1
     IDENTIFY           = 2
@@ -355,7 +356,7 @@ class DiscordWebSocket:
         client: Client,
         *,
         initial: bool = False,
-        gateway: Optional[str] = None,
+        gateway: Optional[yarl.URL] = None,
         session: Optional[str] = None,
         sequence: Optional[int] = None,
         resume: bool = False,
@@ -372,11 +373,11 @@ class DiscordWebSocket:
         gateway = gateway or cls.DEFAULT_GATEWAY
 
         if zlib:
-            url = f'{gateway}?v={INTERNAL_API_VERSION}&encoding={encoding}&compress=zlib-stream'
+            url = gateway.with_query(v=INTERNAL_API_VERSION, encoding=encoding, compress='zlib-stream')
         else:
-            url = f'{gateway}?v={INTERNAL_API_VERSION}&encoding={encoding}'
+            url = gateway.with_query(v=INTERNAL_API_VERSION, encoding=encoding)
 
-        socket = await client.http.ws_connect(url)
+        socket = await client.http.ws_connect(str(url))
         ws = cls(socket, loop=client.loop)
 
         # Dynamically add attributes needed
@@ -577,7 +578,7 @@ class DiscordWebSocket:
             self._trace = trace = data.get('_trace', [])
             self.sequence = msg['s']
             self.session_id = data['session_id']
-            self.gateway = data['resume_gateway_url']
+            self.gateway = yarl.URL(data['resume_gateway_url'])
             _log.info('Connected to Gateway: %s (Session ID: %s).', ', '.join(trace), self.session_id)
 
         elif event == 'RESUMED':