Update module gorilla/mux to v1.8.0

See merge request !12

Configure Renovate

See merge request !10

Fixes issue #16, the only change is in the u2f/otp login links.

Update the crewjam/saml library too.

Enforce group membership checks in the SAML server

See merge request !9

In this scenario there is no need to set 'users_file', instead we
introduce the new boolean attribute 'email_usernames'.

Apparently this is applied even after the redirect, so we can't use it.

Adds the 'base-uri', 'form-action' and 'frame-ancestors' properties.

Do not attempt to call backends (keystore) with empty usernames.

Metrics cover specifically the authentication workflow.

The sess.UserInfo is still unset at that stage, use valid information
instead. This fixes a bug where keys were not being unlocked for users.

Just to cover edge cases when sessions are about to expire.