Cannot upload new image in media library

FWIW this was definitely working during Drupalcon Barcelona in late September so our troubleshooting can be in the mindset of "what broke this" vs. "we need to build this". Typically we'd have had tests that would have caught this, but the challenges of getting this set up in JS e2e tests made it a lower priority. Perhaps a PHP FunctionalJavascript test should accompany this fix as those tests are already equipped to handle file uplaods.

This is due to a change introduced in 🐛 XBEndpointRenderer adds response headers that sometimes exceed common server limits Active , it'll be a quick fix + a little additional time to add tests that prevent this from regressing.

The MR has a fix and a FunctionalJavascript test that verifies it works. Using FunctionalJavascript instead of Cypress E2E allows us to directly test file uploads.

However, as someone not all that well versed in Gitlab CI, I'm having trouble getting the built UI app to be available when the FunctionalJavascript tests run. Anyone is welcome to jump in and address that, and if this sits for too long I'll hit up the Gitlab docs and take care of the rest.

Was supposed to mark as needs work.