db-setup.mysql wrongly uses too long keys

[mid1221213]

The creation of the table authreg with that script fails on my installation (Ubuntu 17.04) with the message ERROR 1071 (42000): Specified key was too long; max key length is 255 bytes.

I don't know where the max key length is set in MySQL, but apparently, according to what I've seen on some Q&As, using keys that long is useless. Manually editing the file db-setup.mysql to modify is simple, but IMHO this file should be changed to not use keys as long as the maximum field size, maybe 50 for example.

FYI, and if I understood correctly, the authreg table as it tries to create it with the original file would use two 255-length keys, that means 2 times 255 times 2 (the last because of UTF8) = 1020 bytes keys.

[lifeofguenter]

Looking at this: https://github.com/jabberd2/jabberd2/blob/master/storage/authreg_mysql.c#L46 it should be configurable, or at least set to a much lower value (maybe max 128?) to realistically fit in mysql with utf8mb