WebAdmin tasks for mail reprocessing

We need a webAdmin frontend for reprocessing emails stored in a MailRepository.

• I propose these endpoints:

PUT mailRepositories/:name/reprocessing?processor=root
PUT mailRepositories/:name/:key/reprocessing?processor=root

(root being the default target processor)

• This will create Tasks handing the reprocessing. This task should be created in data-library to be used potentially by other protocols.

• Unit tests can be done with mocks and should focus on input validation.

We would need to write an integration test for this in mailet integration tests

• root processor would only contain a *ToRepository* mailet
• transport processor would contain normal delivery logic
• We send a mail and await it to be stored in the repository
• We reprocess the mail to the transport processor and await task end
• We verify the mail is well received

We can do the same operation with 2 emails.