Deactivating user doesn't remove external IDs

[ptman]

Description

After deactivating a user (and erasing user data) one cannot sign up a new user using the same account on the same OIDC provider because the external_user_id is still left. It needs to be removed as an extra step.

Steps to reproduce

1. Sign up using e.g. google account
2. Deactivate user
3. Try to sign up again using the same google account

Homeserver

another homeserver

Synapse Version

1.68.0

Installation Method

Docker (matrixdotorg/synapse)

Platform

Ubuntu, matrix-docker-ansible-deploy

Relevant log output

this really doesn't involve log output

Anything else that would be useful to know?

Is this by design?

[clokep]

Is this by design?

Yes, usually if you deactivate a user you do not want that user (that human) on your system. So you don't want future logins to work with the same external login info.

[clokep]

(That being said -- it is possible we should give steps of how to do this in the documentation?)

[ptman]

What about the user deactivating the account themselves?

[clokep]

Duplicate of #11072.