[guild] add support for system_channel_id & GUILD_MEMBER_JOIN

disco/types/guild.py

@@ -268,6 +268,8 @@ class Guild(SlottedModel, Permissible):
         The id of the afk channel.
     embed_channel_id : snowflake
         The id of the embed channel.
+    system_channel_id : snowflake
+        The id of the system channel.
     name : str
         Guild's name.
     icon : str
@@ -301,6 +303,7 @@ class Guild(SlottedModel, Permissible):
     owner_id = Field(snowflake)
     afk_channel_id = Field(snowflake)
     embed_channel_id = Field(snowflake)
+    system_channel_id = Field(snowflake)
     name = Field(text)
     icon = Field(text)
     splash = Field(text)
@@ -468,6 +471,10 @@ class Guild(SlottedModel, Permissible):
     def splash_url(self):
         return self.get_splash_url()
 
+    @property
+    def system_channel(self):
+        return self.channels.get(self.system_channel_id)
+
     @property
     def audit_log(self):
         return self.audit_log_iter()

disco/types/message.py

@@ -22,7 +22,8 @@ MessageType = Enum(
     CALL=3,
     CHANNEL_NAME_CHANGE=4,
     CHANNEL_ICON_CHANGE=5,
-    PINS_ADD=6
+    PINS_ADD=6,
+    GUILD_MEMBER_JOIN=7,
 )