Support session auth

[florianm]

Feature

Support missing API endpoints:

• [ ] https://odkcentral.docs.apiary.io/#reference/authentication/session-authentication/logging-in
• [ ] https://odkcentral.docs.apiary.io/#reference/authentication/session-authentication/using-the-session
• [ ] https://odkcentral.docs.apiary.io/#reference/authentication/session-authentication/logging-out

What would the workflows be like to use session auth instead of basicauth? Would UX be simplified? Would session auth collide with basic auth, or confuse entry level users?