Move MVP

* update User model to allow for moved_to and also_known_as values
* allow users to add aliases (also_known_as) in UI
* allow users to move account to another one (moved_to)
* redirect webfinger to the new account after a move
* present notification to followers inviting to follow at new account

Note: unlike Mastodon we're not running any unfollow/autofollow action here: users can decide for themselves
This makes undoing moves easier.

TODO

There is still a bug with incoming Moves, at least from Mastodon.
This seems to be something to do with Update activities (rather than Move, strictly).

bookwyrm/forms/edit_user.py

@@ -70,6 +70,22 @@ class DeleteUserForm(CustomForm):
         fields = ["password"]
 
 
+class MoveUserForm(CustomForm):
+    target = forms.CharField(widget=forms.TextInput)
+
+    class Meta:
+        model = models.User
+        fields = ["password"]
+
+
+class AliasUserForm(CustomForm):
+    username = forms.CharField(widget=forms.TextInput)
+
+    class Meta:
+        model = models.User
+        fields = ["password"]
+
+
 class ChangePasswordForm(CustomForm):
     current_password = forms.CharField(widget=forms.PasswordInput)
     confirm_password = forms.CharField(widget=forms.PasswordInput)