fix: handle public_flags value for Message.author when member cac…

…he is disabled (#870)

The `Message.__init__ -> Message._handle_member -> Member._from_message`
path calls `User._to_minimal_user_json`, which previously didn't copy
over the user's `public_flags` value.
With the member cache (and therefore also the user cache) enabled, this
isn't an issue as `Member.__init__` uses the cached user and not the
(previously incomplete) user data. With the cache disabled, the user
data gets parsed, which didn't include that value.

To reproduce, just `print(ctx.author.public_flags)`.

Co-authored-by: arl <me@arielle.codes>
Signed-off-by: arl <me@arielle.codes>

changelog/870.bugfix.rst

@@ -0,0 +1 @@
+Fix :attr:`Message.author.public_flags <Member.public_flags>` always being ``0`` when the member cache is disabled.

disnake/user.py

@@ -121,6 +121,7 @@ def _to_minimal_user_json(self) -> UserPayload:
             "avatar": self._avatar,
             "discriminator": self.discriminator,
             "bot": self.bot,
+            "public_flags": self._public_flags,
         }
 
     @property