Support MSC2530 fields in media event types

Add `filename`, `format` and `formatted_body` to media event content
types.

Signed-off-by: Joe Groocock <[email protected]>

Author: frebib

mautrix/types/event/message.py

@@ -272,12 +272,13 @@ class LocationInfo(SerializableAttrs):
 
 
 @dataclass
-class MediaMessageEventContent(BaseMessageEventContent, SerializableAttrs):
+class MediaMessageEventContent(TextMessageEventContent, SerializableAttrs):
     """The content of a media message event (m.image, m.audio, m.video, m.file)"""
 
     url: Optional[ContentURI] = None
     info: Optional[MediaInfo] = None
     file: Optional[EncryptedFile] = None
+    filename: Optional[str] = None
 
     @staticmethod
     @deserializer(MediaInfo)