This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
A generic implementation of Auth::Authenticator which stores data in the
new UserAssociatedAccount model. This should help significantly reduce the duplicated
logic across different auth providers.
At the moment core providers are hard-coded in Javascript, and plugin providers get added to the JS payload at compile time. This refactor means that we only ship enabled providers to the client.
