Email blocklisting (#718)

* Interface complete for the email blacklisting

* Everything seems to work

* Neutralize language

* fix clippy warnings

* Add missing spaces

* Added matching test

* Correct primary key datatype for postgresql

* Address review comments

* Add placeholder when empty. Fix missing 'i'

templates/instance/users.rs.html

@@ -12,6 +12,7 @@
         (&uri!(instance::admin).to_string(), i18n!(ctx.1, "Configuration"), false),
         (&uri!(instance::admin_instances: page = _).to_string(), i18n!(ctx.1, "Instances"), false),
         (&uri!(instance::admin_users: page = _).to_string(), i18n!(ctx.1, "Users"), true),
+        (&uri!(instance::admin_email_blocklist: page=_).to_string(), i18n!(ctx.1, "Email blocklist"), false)
     ])
 
     <form method="post" action="@uri!(instance::edit_users)">