Merging accounts

[michielbdejong]

Scenario:

• a user logs in with Slack -> session id 1
• they log out
• now they log in with Solid -> session id 2
• then they log in with Slack again -> update all occurrences of session id 1 to become session id 2

Does this make sense?

[michielbdejong]

OK, now another scenario:

• log into Slack on device A -> session id 1
• log into Solid on device B -> session id 2
• log into Slack on device B -> update all occurrences of session id 1 to become session id 2
• the session on device A is broken

To deal with this, the identities table should link between identities and accounts,
and the sessions table should link between sessions and accounts, and then we merge the accounts instead of the sessions.

[michielbdejong]

Hm, actually having the indirection through accounts is one option.
Another option is to keep accounts and sessions equivalent, and when sessions merge, update all current session ids (through a websocket push? or through a special database table that looks up old session id -> new session id?)

[michielbdejong]

In any case it's something we can leave for later, not necessarily in scope for #3.

[michielbdejong]

Merging this issue back into tubsproject/reflector#17.