Decompose and/or add more tests for CampaignDetails

Created by: sqs

When I have gone to make edits (for prototyping purposes) to CampaignDetails.tsx, I am nervous because it is long/complex and lacks test coverage for actions (eg creation, editing, saving, etc.).

It would be nice if it were decomposed into more smaller and simpler components, and if there was more test coverage. Don't do this just on my account, but if you were already thinking of this, consider this a +1 for it.