Missing blacklisting handlers in DBManager

[karelpak1]

Describe the bug
Missing handlers in DatabaseManager regarding blacklisting + schema? Which means, blacklisting is practically not functional. Also I read updates.md and this feature was removed (why?) in 6.0.0, sadly code is still present (in owner cog) and should be removed, if not planned for future use.

To Reproduce
Steps to reproduce the behavior:

1. /blacklist add {user}
2. /blacklist remove {user}
3. /blacklist show
4. See all errors

Expected behavior
Add/remove user to blacklist.
Show users in blacklist.

Screenshots
None

Template Version
6.1.1 - 1bb7963

Additional context
None

[karelpak1]

What is your plan @kkrypt0nn? Add blacklist support back or remove it completely? I can easily make a PR with added blacklist support. I've already tested it and practically it's taken from the old version of db_manager and everything rewritten in database init.

[kkrypt0nn]

Planned to remove it, as it was my intention - there's no real reason to have blacklists especially storing them in a database like I previously did.

The problem is resource-wise it's not smart to make a database query every time a message is sent or slash command is executed. If someone wants to have one, would make sense to hard-code the IDs and check with those rather than making database queries.