This reverts commit 5045f9e188 because the main stakeholder isn't using the feature and it's putting a strain on email server accountability vis-a-vis spam lists.
# Conflicts:
# src/Moderation/DomainPatternBlocklist.php
- added missing type-hints
- added documentation
- removed parameter $baseURL while it can be locally get the same way but
lesser parameter
- used ActivityNamespace::SALMON_ME
- changed double-quotes to single