Set required role

[Johnnycyan]

What cog is this feature request for?

Birthday

Describe the feature request in as much detail as possible

Ability to set a required role for a user to have a birthday set. If they lose the role, remove their birthday from the bot.

In a server I manage we use the birthdays as a Twitch subscriber perk (and to not clutter it). The problem is, if subs set their birthday and then stop subbing the bot will continue to announce their birthday in a channel they can't access.

So ideally either add the ability to prune the birthday db by required role or just add the option to check for a specific role and if they don't have it, then don't post the birthday message.