Attachments file size is hard limited

Attachments file size is hard limited to 42MB.

https://github.com/frab/frab/blob/cbe681c60e8f5734acf10f116a8d8acefebd2498/app/models/event_attachment.rb#L6

@manno is there a reason to this specific limit? (i.e. something bad will happen if we try to store larger files)

Can we make this configurable?