In this change, we wire up a new NeoPass OAuth2 strategy for OmniAuth,
and hook up the "Log in with NeoPass" button to use it!
The authentication currently fails with `invalid_credentials`, and
shows the `owo` response we hardcoded into the NeoPass server's token
response. We need to finally follow up on the little `TODO` written in
there!
If you pass `?neopass=1` (or a secret value in production), you can see
the "Log in with NeoPass" button, which currently takes you to
OmniAuth's "developer" login page, where you can specify a name and
email and be redirected back. (All placeholder UI!)
We're gonna strip the whole developer strategy out pretty fast and
replace it with one that uses our NeoPass test server. This is just me
checking my understanding of the wiring!
