Build a server to generate authorization TANs for upload

[antonxy]

We discussed creating a separate server for generating the upload TANs.

Current Idea:

• The authorization server should give out QR Codes containing the TANs on request to health authorities/laboratories (For now to everyone (testing purposes))
• The authorization server should remember which TANs it produced
• The TCN server can ask the authorization server if a TAN is valid
• The TCN server can ask the authorization server to mark a TAN as used (can not be used to upload again)

Things we need to do:

• Code for database connection - Use posgres again, since we are already using that for the backend
• Authentication for the TCN server - TLS client certificate auth with pinned pubkey?
• Authentication for health authorities - maybe using electronic health card?

[ChristianRomberg]

Did a very rudimentary implementation. The psql connection is up and working, though tests still have to be done