feat: create a dialog to downgrade own membership

[LinaYahya]

No description provided.

[spaenleh]

🌷 Thank you for this change.

I understand dis-allowing a user to edit their own permission is the safest way to ensure they do not loose access. But I think we should let users downgrade their permission if they want.

Just to recap:

• users that can edit memberships: only admins
• users that could downgrade their membership: only admins

Currently with the flick of a select you can remove your membership, it is too easy can have destructive and unforgiving consequences. I think we should introduce the dialog as a way to warn the user that they might do something that they can not undo. So I would change it so that they can downgrade their permission but only after having seen the dialog and accepting the consequences.

Also important is that they should not be able to downgrade their permission if they are the last admin.

[spaenleh]

Just two comments about the version, otherwise it is good to merge once you have updated them.