refs https://github.com/TryGhost/Product/issues/3349
- added a download handler for the analytics download button.
- wired up the download api endpoint
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### <samp>🤖 Generated by Copilot at 46054be</samp>
This pull request adds a feature to export post analytics as a csv file
from the membership analytics dashboard. It implements a new query hook,
a download function, and a response handler in the
`apps/admin-x-settings` app, and adds a test case for the feature.
refs https://github.com/TryGhost/Product/issues/3349
- Simplified a few more places after switching to react-query
- Improved how mocking works in specs to be more scalable as the number
of queries increases
refs https://github.com/TryGhost/Team/issues/3349
Tidies up the remaining major pieces which were not covered by tests.
Extends the existing test patterns, although the API mocks are getting a
bit unmanageable.
