Account Manager

[dholms]

This replaces the ServiceDB with an AccountManager abstraction

There are a few motivations involved in this:

• we were down to only two services in the PDS (account & auth) so it made sense to combine them in an abstraction
• Some PDSs may rely on an "entry way auth service". This abstraction should make it easier to work that service into the PDS without having complex switch logic in the routes
• Concurrency concerns are very different with a single SQLite DB vs Postgres

The third point influenced the design of the AccountManager: database transactions are never exposed to routes, it is the AccountManager's prerogative to wrap transactional db queries within an abstraction. Routes should be able to call any function on the AccountManager without worrying about transactions locking.

I reworked many of the longer transactions (such as create account & refresh session) to do as much work ahead of time outside of the transaction, then do all of it's transactional writes quickly in "parallel".

I decided to take a slightly different approach with the code here. Instead of having services with a stateful db varaiable, I have files of "helper functions" that wrap a single postgres query. Then the AccountManager maintains a reference to the "AccountDB" and composes those helper functions into it's interface (sometimes just passing through directly to them)

[devinivy]

Looking good, real smooth!

[dholms]

you can see how i handle racing refreshes here