migrate airflow/superset oidc to use email for default usernames

[michaeljguarino]

Use Case

Plural usernames are changeable but are currently being used as the flask appbuilder username which the underlying code doesn't know how to modify. We'll want to write a migration to modify these to something more stable and avoid this potential footgun.

Ideas of Implementation

Modify oauth provider subclass and write a migration job to do the database rewiring.

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