Add backend snapshot tests for task assignment

[normanrz]

Currently, the backend snapshot tests don't cover tasks.
Cases that could be tested:

• Creating tasks
• Requesting tasks
• Peeking next tasks
• Requesting tasks with different project priorities
• Shouldn't receive tasks from paused projects

Log Time

[hotzenklotz]

Related to #2190

[daniel-wer]

I just stumbled upon this issue and wanted to document the current state. The first three are covered by the e2e tests by now, the other two would be a good addition :)