Commit b7896b3153 moved events.go from the 'authenticate' package to
'internal/authenticateflow' in order to avoid an import cycle. However
this location is not actually suitable, as the hosted authenticate
service refers to AuthEvent and AuthEventFn.
Move events.go back out from under 'internal', to a new package
'authenticate/events'. This should still avoid an import cycle between
'authenticate' and 'internal/authenticateflow', while also allowing the
hosted authenticate service to use the events types.
Add a new Stateful type implementing the stateful authentication flow
from Pomerium v0.20 and earlier.
This consists mainly of logic from authenticate/handlers.go prior to
commits 57217af and 539fd51.
One significant change is to set the default IdP ID when an IdP ID is
not provided in the request URL (e.g. when signing in directly at the
authenticate service domain). Otherwise, if session state is stored with
an empty IdP ID, it won't be valid for any route.
Move the Stateless.logAuthenticateEvent() method into the main
stateless.go file.
(This was in events.go temporarily so that Git would track the file
history as a rename from authenticate/events.go.)
Consolidate all logic specific to the stateless authenticate flow into a
a new Stateless type in a new package internal/authenticateflow. This is
in preparation for adding a new Stateful type implementing the older
stateful authenticate flow (from Pomerium v0.20 and previous).
This change is intended as a pure refactoring of existing logic, with no
changes in functionality.
