Optimize layers API endpoints

[Chatewgne]

Split /api/geolayer/view/{view_slug}/ into 4 endpoints :

• /api/geolayer/view/{view_slug}/
• /api/geolayer/view/{view_slug}/layersTree/layer/{id}
• /api/geolayer/view/{view_slug}/customStyle/layers/{id}
• /api/geolayer/view/{view_slug}/customStyle/source/{id}

⚠️ Breaking changes :

• customStyle data has been moved from /api/geolayer/view/{view_slug}/ to /api/geolayer/view/{view_slug}/customStyle/layer/{id} and /api/geolayer/view/{view_slug}/customStyle/source/{id}
• layers data has been simplified in /api/geolayer/view/{view_slug}/ and the full content has been moved to /api/geolayer/view/{view_slug}/layersTree/layer/{id}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.44%. Comparing base (8af4689) to head (72ce90c).
⚠️ Report is 62 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1127      +/-   ##
===========================================
+ Coverage    96.18%   96.44%   +0.25%     
===========================================
  Files           86       87       +1     
  Lines         4222     4441     +219     
===========================================
+ Hits          4061     4283     +222     
+ Misses         161      158       -3     

Flag	Coverage Δ
backend-unittests	96.44% <100.00%> (+0.25%)	⬆️

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[Bo-Duke]

@Chatewgne I updated the front submodule to the branch in visu-front that handles the slip endpoints without breaking everything.

Currently it sends all the requests all at once at load so it's good enough to test but not ready for a merge yet. Terralego/visu-front#225

[Bo-Duke]

@Chatewgne I did a back-end change! 😱😱😱😱

I just needed the variables in the split endpoint, but I don't know if that's the way to do it or if tests are needed

(It did work well enough for my tests though)

[Bo-Duke]

Added optim_split_endpoints to release.yml to test deployments, branch must not be merged with this change still here.