The MailPlugin collaborator returned results for both user and mail
collaborators, but it was registered only for mail collaborators. While
it might make sense to move the user results to the UserPlugin instead
that change would be more complex and riskier, so for now the MailPlugin
is now registered for both user and mail collaborators and the results
are limited only to the registered type.
As the plugins are registered only with their class and then resolved
when needed using dependency injection it is not possible (as far as I
know) to provide an explicit parameter in the constructor to
differentiate whether the MailPlugin should return user or mail
collaborators. To overcome this two subclasses are introduced,
MailByMailPlugin and UserByMailPlugin, which just hardcode in their
constructor the collaborator type that their parent MailPlugin must use,
and those subclasses are the ones registered instead of the MailPlugin
(which still contains all the logic).
Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>
