Replace Birthdaybot with our own

[adrian-goe]

We currently use birthday bot do give the birthday role.
Since we can now use cron, we want to do this in our bot now.

The Bot should check all 30 (maybe 15 -> Australia) mins, if a user has now his birthday. Be aware of the different time zones.

After 24h, the birthday role should be removed by the bot.

[adrian-goe]

So we figured out, that we have stored some timezones in the database, but in text form. Some users don't have a timezone.

[mvarendorff]

Going through that list, it appears that those users had their birthday set with an old version of the birthday command. I went through the list by hand and BirthdayBot reported not having birthday data for any of them.

Given that those members don't receive the Birthday role anyway atm, I don't mind still moving forward with this though. We should think about a way of notifying those members about the situation and ways to set their timezone and expect null values in the timezone field when implementing our own birthdaybot version.