Consider a refactoring of the sending system #5
Description
I only have a few users with which the current implementation does not cause any problems, but I am concerned about performance on a larger user base. It would probably be wise to consider a refactoring of the sending system to perform fewer calculations per user.
In addition, the current send is limited by the execution time. Even if my system was as optimized as possible (which is not the case), the number of recipients is still limited by the execution time. It would therefore be necessary to send the emails in the background. (This issue also affects Webtrees, see this issue)