Use mag in data requests, no more zoomStep/exponent

[fm3]

• use mag instead of zoomStep in data requests
• start renaming some resolution and zoomStep to mag in the backend internally (some places still use resolution)
• remove unused datastore routes
• clean up thumbnail management (no more json with base 64 encoding)
• fixed the snapshot tests, see discussion below

URL of deployed dev instance (used for testing):

• https://datarequestmag.webknossos.xyz

TODO

• frontend should send mag when requesting
  • data (normal bucket request) (also in volume annotations)
  • data (rawCuboid)
  • isosurfaces
• wkconnect should also be adapted Adapt to wk-datastore api version 2.0 (mag replaces zoomStep, thumbnail.jpg) webknossos-connect#129
• bump datastore api version

Follow-Up

• wk python client should also be adapted (uses rawCuboid GET) Adapt to new datastore API (mag instead of zoomStep) webknossos-libs#719 – this is currently backwards compatible, but I want to remove that optional parameter here eventually, tracked in Remove zoomStep entirely, after client has been updated #6189

Steps to test:

• Load some data, isosurfaces
• use rawCuboid via frontend API, request dataset thumbnail

Issues:

• contributes to Consistent Terminology #6053
• fixes bucket requests: replace zoomStep by actual (vec3) mag  #4893

---

• Updated (unreleased) changelog
• Updated (unreleased) migration guide if applicable
• Adapted wk-connect if datastore API changes
• Needs datastore update after deployment
• Ready for review

[daniel-wer]

@fm3 I'm not sure whether I got everything, but I switched the bucket request, the ad-hoc isosurface computation request, and the data cuboid request code. In my testing all of these work as expected, again. However, I'm not sure whether there's more interfaces that have changed.

[daniel-wer]

I also just noticed that the snapshot tests were not doing anything, because the snapshots were missed to move when the test directory was changed in #6065 /cc @philippotto. I corrected that, let's see whether any errors pop up.

Edit: I added a82b6a1 so that this won't happen in the future. If a snapshot doesn't exist and the tests are run in a CI environment, the tests will fail.

[jstriebel]

Awesome stuff, huge fan of the restructured datastore API ❤️
The backend changes look very good to me, props for using mags consistently, this helps readability in several places!

[MichaelBuessemeyer]

The frontend part looks fine to me 👍 🔍 🚀

[MichaelBuessemeyer]

Nice refactoring 👍

[MichaelBuessemeyer]

I just noticed that this method isn't used anywhere. Only getLowestResolution is being used.

But I think it is fine to keep this method in case someone wants the highest resolution in the future.