The tests had very much duplication and some if it was even wrong! For
instance, `withRcloneEnv` in the MySQL test didn't have the `"$@"` at
the bottom to execute commands passed to it. Because of that, the MySQL
testcase never checked whether files can be uploaded.
Since tests are just another module-system I decided to abstract away
common things by using it:
* Define a base module with
* an empty `client` node and a `nextcloud` node with defaults
shared among all tests.
* rclone scripts that are used by all tests.
* a `testScript` checking upload/download. Additional checks can be
added via `test-helpers.extraTests`.
* Make common information such as admin user & password shared via
options.
Also, changed the following things:
* The `name` of the final derivation also includes the Nextcloud major
it was tested against.
* Improved the objecstore test by making sure the file was actually
uploaded into the bucket.
* Make sure `withRcloneEnv` actually invokes the command it gets as
`argv`. Until no, nothing was uploaded. This mistake was copied from
the MySQL test that appears to have the same issue (will be addressed
in the next commit).
* Test upload/download through with rclone once to see if Nextcloud
interaction with S3 works fine.
* Make sure we actually have something in the bucket (until now with an
`ls` and no real check, will do some larger cleanups and make this
better in the next commit).
* Use actual AWS-style access keys.
