Server backend E2E testing

[gjedlicska]

Our current automated testing strategy only covers the server component.
This causes some uncertainty in the team resulting in increased manual testing time needed when upgrading components like the file import service or the preview service.

The conceptual workflow below would cover a very big portion of the current server backend functionalities:

• create a new user on the server
• create a new stream
• create a basic webhook and register a local listener
• subscribe to various events ( branch, commit create etc)
• trigger a file import
• wait for the file import to finish, verify the created commit root object id to a pre-baked object id
• wait for the preview of the commit to be generated (prob its too hard to verify the content)
• verify the results of the subscriptions
• wait for the register webhook callbacks and verify their content
• delete the stream

This workflow could be implemented with one of our SDKs and as a stretch goal could also be turned into an automated K8s test job, which we run on every PR and newly deployed server.