Add auth method to authentication state.

[sea-snake]

Add auth method to authentication state, this will be used in the dashboard to indicate which access method is currently in use.

The last used identity store data could also be used for this purpose but isn't reliable since it's value could change by signing in on other tabs/windows due to it being tied to local storage.

Changes

• Add authMethod property to authentication store state.
• Update flows to pass auth method into authentication store.
• Remove unused confirmationCode from authFlow.

Tests

Verified authentication flows still work as expected and correct auth method value is present when expected.