docs: detail how to mount and use external drivers

[adwk67]

Description

docs: detail how to mount and use external drivers. fixes https://github.com/stackabletech/hive-operator/issues/416.

Definition of Done Checklist

• Not all of these items are applicable to all PRs, the author should update this template to only leave the boxes in that are relevant
• Please make sure all these things are done and tick the boxes

# Author
- [x] Changes are OpenShift compatible
- [x] ~Integration tests passed (for non trivial changes)~ Tested with integration test in local branch

# Reviewer
- [ ] Code contains useful comments
- [ ] Code contains useful logging statements
- [ ] (Integration-)Test cases added
- [x] Documentation added or updated. Follows the [style guide](https://docs.stackable.tech/home/nightly/contributor/docs-style-guide).
- [x] Changelog updated
- [x] Cargo.toml only contains references to git tags (not specific commits or branches)

# Acceptance
- [ ] Feature Tracker has been updated
- [ ] Proper release label has been added
- [ ] [Roadmap](https://github.com/orgs/stackabletech/projects/25/views/1) has been updated

[adwk67]

@maltesander I have a local integration test for this. What do you think - shall I push that too and just leave it commented out of the test definitions (so it can be activated as necessary)? I wouldn't leave it active as we would either have to upload the mysql driver to Nexus or have an external dependency.

[fhennig]

I wanna look at it more in depth, but already I'd like the fileame to just be database-driver.adoc and also if you could put linebreaks between sentences (so each sentence is on its own line) that would be great!

[maltesander]

@maltesander I have a local integration test for this. What do you think - shall I push that too and just leave it commented out of the test definitions (so it can be activated as necessary)? I wouldn't leave it active as we would either have to upload the mysql driver to Nexus or have an external dependency.

I dont think its in scope here, but having an integration test (could be an existing one) switching to mysql for testing would be nice :)

[fhennig]

I think it's a good idea to document the alterantives as well, but it wasn't part of the original scope ofthe ticket. But ideally we'd lay out the options for the users, and then they can decide (Do I want to host an image somewhere? Can I use ReadWriteMany? etc)

[sbernauer]

I also volunteer to quickly throw the Dockerfile together, I don't want to put the burden on @adwk67. Shall I do that?

[adwk67]

I've documented it here 64754ea but couldn't get it to work yet. Maybe we can take a look together @sbernauer ?

[adwk67]

ok, got it working now.