Login: allow to change login method inside auth modal

Allow to change the login method, from the auth modal (like in Cesium v1)

added Authentication Doing labels

assigned to @blavenie

changed milestone to %2.0.0-alpha40

mentioned in commit 54a70471

mentioned in merge request !20 (merged)

mentioned in commit 3bb49f43

mentioned in commit 6dd530a2

closed