fixes #828

fixes #826

Closes gh-815

closes #806

closes #805

Since the principal not necessarily is json-searializable we need to
avoid this and just pass the wanted properties to thymeleaf

fixes #799

When the base-path for the actuator is set to `/` on spring boot 2 the
endpoints can't be queried via the actuator index and need to be probed.
Therefore we need to probe not only for the old names but also for the
names in boot 2.0.

fixes #793

closes #792