feat: replace authbackend with keycloak and adapt frontend accordingly

Right now the auth backend does not comply security standards (eg. FIPS); exising solutions (like keycloak.org) do out of the box and are open source

added Enhancement In progress backend labels

assigned to @m.behrisch

added #29 (closed) as child task

added #30 (closed) as child task

marked this issue as related to #31

mentioned in commit 34506174

mentioned in merge request !28 (closed)

added Upcoming label and removed In progress label

marked this issue as related to #26

mentioned in commit c45ffe10

mentioned in merge request !33 (merged)