feat(schematic): integration testing

[andrewelamb]

This is identical to #2398 plus some fixes to the testing workflow.

This PR chas a new wrokflow that is trggred when PRs are made from the new Schematic-API-Staging branch into main.

This PR:

• fixes fds-1288
• fixes fds-1288
• PRs are now done from forks to Schematic-API-Staging instead of main
• PRs to Schematic-API-Staging only trigger tests that don't require secrets
• PR's are then don form Schematic-API-Staging to Main
• A new workflow that triggers when PRs are done from Schematic-API-Staging to Main that runs all tests has been added
• All non synapse tests are not mocked at all
• A new set of tests test_synapse_endpoints.py has tests for all synapse endpoints where nothign is mocked
• handle_exceptions is now tested directly
• When the schema url isn't correct an InavlidSchemaURL exception is now raised
• handle exceptions returns a 404 status when InavlidSchemaURL is caught

[andrewelamb]

@tschaffter @GiaJordan Can I get your approval on this?

[GiaJordan]

approving per discussion on slack with @andrewelamb

[tschaffter]

• Can you please add a high-level description of what this PR is doing? When is this workflow being triggered?
• Why does the title of the PR includes "(feat(schematic): integration testing #2398)"?
• The new GH workflow duplicates parts of the CI workflow common to all projects. This would lead to a waste of resources. Based on previous discussions, you may want this PR to focus on integration testing for Schematic. Also, now or in another PR, you could consider running it AFTER the common CI workflow successfully passes, so that e2e testing is not run if the linting check fails, for instance.

[andrewelamb]

@tschaffter

Can I get rid of the push job in the new workflow? That seems redudant.

"The new GH workflow duplicates parts of the CI workflow common to all projects. This would lead to a waste of resources."

What parts cna I get rid of in the pr job in the new workflow? My understanding is almost all of it is needed to for the e2e testing to work. I could get rid of the Lint the affected projects step since the main CI workflow will check that, and the Set up Renv cache since the API won't use that. What other steps can go?