Inviting lots of peer reviewers at once is slow

[ajrbyers]

Is your feature request related to a problem? Please describe.
Some journals have to invite large numbers of peer reviewers in order to get an adequate response.

Describe the solution you'd like
Add a new system by which an editor can invite a large number of peer reviewers with a customisable “reason” field that can be used to individualise the email template.

Describe alternatives you've considered
N/a

Additional context
This is required for RR/ID.

[ajrbyers]

Closed by #3490