Add Docker and Papercut support, configure email server via appsettings, and fix IEmailSender implementation for functional tests

[eduardogoncalves]

This pull request adds support for Docker and Papercut, making it easier for developers to test and run the application in a containerized environment. Allows email server configuration via appsettings:

Fixes the implementation of the IEmailSender interface during functional tests by adding a new FunctionalTestInfrastructureModule that uses FakeEmailSender implementation, ensuring that functional tests do not actually send emails to real email addresses.

[ardalis]

Sorry, v8 update messed with a bunch of your changes. I'd still pull them in for 8.1 if we can sort out the conflicts, though.

[ardalis]

I've added mailserver configuration but am going to forego the docker additions.