Enable Celery Background Manager for additional Backends

[datenzauberai]

Start with a description of this PR. Then edit the list below to the items that make sense for your PR scope, and check off the boxes as you go!

Contributor Checklist

• I have broken down my PR scope into the following TODO tasks
  • task 1
  • task 2
• I have run the tests locally and they passed. (refer to testing section in contributing)
• I have added tests, or extended existing tests, to cover any new features or bugs fixed in this PR

optionals

• I have added entry in the CHANGELOG.md
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  • this GitHub #PR number updates the dash docs
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[camdecoster]

Thanks for creating this PR! Is it in a state where we can review it?

[datenzauberai]

Thanks for creating this PR! Is it in a state where we can review it?

I'm on it, but this still needs work! The manager itself works locally, but I want to have good tests first so that this can be maintained in the future.