[ENG-4961] Make Owncloud configurable via api v2

[Johnetordoff]

Purpose

Make Owncloud fully configurable via the API v2.

Changes

• override the serializer to allow users to update the owncloud credentials addons/owncloud/README.md

QA Notes

Please make verification statements inspired by your code and what your code touches.

• Verify
• Verify

What are the areas of risk?

Any concerns/considerations/questions that development raised?

Documentation

Side Effects

Ticket

https://openscience.atlassian.net/browse/ENG-4961