Add settings to specify SSL cert and key for DB server

What does this MR do?

Expose settings to configure SSL certificate and key for a database server, if an external one is used.

Related issues

#4296 (closed)

Checklist

See Definition of done.

• Changelog entry created. Not applicable for Documentation changes and minor changes.
• Tests added
• MR targeting master branch
• MR has a green pipeline on GitLab.com
• trigger-package has a green pipeline running against latest commit

Reviewer Checklist

In addition to above, reviewer must:

• Pipeline is green on dev.gitlab.org if the change is not touching documentation or internal cookbooks