Use relative links to repository files in documentation

See merge request !64

Also block local access using IPv6

See merge request !63

Rename CI repository variable for GitLab 9.0+

See merge request !62

Migrate to Pac4j framework for OAuth handling

See merge request !59

Since we do not use a SecurityFilter, the previously visited page is not
saved in the session.

This improves/fixes compatibility with third-party OAuth APIs.

Improve handling of context path prefix

See merge request !61

Consistently prioritize the `api.path` setting before falling back to
`servletContext.getContextPath()`.

Filter sessions on the DB side to check if key is available

See merge request !58

Daniel Gerhardt authored 7 years ago and Daniel Gerhardt committed 7 years ago

This should massively reduce the time needed for session creation.
Additionally, the `Transactional` annotation has been removed because
it did not have any effect in this case.

Log level for DB logging was overriden by the fallbacki value in some
cases.

ARSnova no longer supports JDK 7 which is still the default for
Travis CI Java builds. `sudo` is disabled to speed up the build start up
time.

Exception logging

See merge request !54

Add messages to exceptions and slightly refactor exception handling.

Exceptions are now always passed to the logger. The logger decides based
on configuration whether and how they are logged. Logging messages were
adjusted for consistency.

Improve exception handling

See merge request !52