Adding guild-utility related functions

[spifory]

As the current production bot has features such as 'auto-role', automated-welcome and leave messages, a private-support('ticket') system, etc. The rewrite should contain the same features.

Automated-Role Adding

This should work using an on_member_join listener of course, and it should basically grab the role ID from the database, and add it to the new member that has joined. HOWEVER, there are times where guilds have what is known as Membership Screening, so if the role gets added and the member has not passed it, the role being added means they get to bypass it.

So, we should check first IF the member has passed the screening yet, and then we can add the role to them, however most guilds may not have that enabled, so I would guess that it would just add the role to the member on join, and not worry about any of the Screening type of stuff.

Private Support

This should create a private channel between the staff members, and the creator of the ticket.

Customizable featues:

• Allow guild owners/admins to set what specific roles can view the channel
• Allow guild owners/admins to limit how many tickets the member is permitted to opening. Should default to 1 in my opinion
• Allow guild owners/admins to allow/deny who(including the ticket author) can close the ticket.

Automated Messages on Leave/Join

This should send a message/embed stating that a new member has joined, or has left the guild. This can either send the message on join, or if Membership Screening is passed, but I feel that the Screening should be passed first, but I am opened to opinions. This should also raise some sort of error if the message is longer than what Discord allows us to use, disnake.ext.commands.String recently came out on the development version, so we could utilize that.

Customizable features:

• Allow guild owners/admins to specify whether this is in an embed or just a normal message
• Allow guilds to state whether Membership screening should be passed BEFORE the message is sent or not. (Still opened to opinions about this though)

I also think we should use disnake-ext-formatter for this, or we could make our own safe way for this, just to avoid any security issues if the member knows how to do these types of things.