Starting with Rclone v1.63, which is used in the Nextcloud tests for
synchronization, the client relies on the correct WebDAV endpoint url,
see https://github.com/rclone/rclone/issues/7103
* Ensure that the redis cache is actually used in the "trivial" case
(`with-postgresql-and-redis`)
* Test against all Nextcloud versions we've packaged
* Actually set a secret to make sure that the provided secret is
properly read by Nextcloud.
* Add myself as maintainer to the secret-test to make sure that I don't
miss any more changes like this that could break the functionality of
that feature.
One of the main problems of the Nextcloud module is that it's currently
not possible to alter e.g. database configuration after the initial
setup as it's written by their imperative installer to a file.
After some research[1] it turned out that it's possible to override all values
with an additional config file. The documentation has been
slightly updated to remain up-to-date, but the warnings should
remain there as the imperative configuration is still used and may cause
unwanted side-effects.
Also simplified the postgresql test which uses `ensure{Databases,Users}` to
configure the database.
Fixes#49783
[1] https://github.com/NixOS/nixpkgs/issues/49783#issuecomment-483063922
