Consolidate insight api

[EDsCODE]

Changes

Please describe.

• updates API to use /insight/{entity_type}

If this affects the front-end, include screenshots.

Checklist

• All querysets/queries filter by Team (if this PR affects any querysets/queries)
• Backend tests (if this PR affects the backend)
• Cypress E2E tests (if this PR affects the front and/or backend)

[timgl]

I think this looks good and everything works. I am a little concerned about having no tests for the insights endpoint. Worth adding some?