Description of the change

Let's add support for Collabora as a subchart. Here's their helm chart and here's their docs.

• Split from Feature request: adding support for document server inside the helm chart #214

Benefits

Allow users to have a document server deployed in this stack.

Possible drawbacks

• Another thing to support.
• Unknown: Not sure how much we can facilitate actually configuring the connection between Nextcloud and Collabora 🤷

Happy to discuss anything further!

Tasks

These are the tasks that would need to be done for this issue to be considered complete:

• add tests in ci and/or helm unit-tests
• add Collabora as a configurable sub-chart via parameters in values.yaml
• install the app is there is one?

We can add more tasks if needed.