* Separate code for proton callback handler
* Upgrade migration
* Use simple_login endpoint from Proton API
* Remove unused classes
* Rename Dto class to Data
* Push rename
* Moved link to PartnerUser to allow subscriptions to depend only on it
* Fix test
* PR comments
* Add unique user_id constraint to PartnerUser
* Added more logs
* Added more logs
Co-authored-by: Adrià Casajús <adria.casajus@proton.ch>