Improve meeting invitation email performance

Is your feature request related to a problem? Please describe.

Yes.

When a user creates or updates an event with lots of participants there is a long delay before the event is saved and the modal closes.

This is partially caused by the sending of invitations... as some steps in the saving process... involve the sending of messages using either the system mailer or a mail provider.

This process is not very noticeable with a small amount of participants, but becomes slower and slower as the number of participants grows.

Describe the solution you'd like

There are some options to improve this with task processing,

a) remove the generating and sending of emails from the saving process, by creating a background task processing job to generate and send messages.

b) remove the sending of emails from the saving process, we can still generate emails during the saving process, but do not directly connect to the mail server and send them during the saving process, instead create a task for each message to be sent using task processing.

In both these cases the downside would be a small delay between saving and sending, we would also need to update the event again to update sending status, or notify the user using the notification interface is something went wrong.

Describe alternatives you've considered

No response

Additional context

No response