Image overlay offering for collection atom publication

[emmanuelmathot]

This PR adds the possibility to add an image overlay offering in the publication of a STAC Collection to an Atom Item

[codecov-commenter]

Codecov Report

Merging #29 (d6ed64d) into develop (42c4fc0) will decrease coverage by 0.06%.
The diff coverage is 23.33%.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #29      +/-   ##
===========================================
- Coverage    56.08%   56.02%   -0.06%     
===========================================
  Files          237      237              
  Lines        34185    34244      +59     
  Branches      2883     2895      +12     
===========================================
+ Hits         19172    19185      +13     
- Misses       15012    15058      +46     
  Partials         1        1              

Flag	Coverage Δ
unittests	56.02% <23.33%> (-0.06%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...s.Data/Translators/StacItemToAtomItemTranslator.cs	85.41% <ø> (ø)
src/Stars.Data/Model/Atom/StarsAtomItem.cs	74.25% <17.14%> (-4.60%)	⬇️
...rs.Data/ThirdParty/Publication/GeosquareService.cs	20.62% <17.64%> (-0.25%)	⬇️
src/Stars.Services/Model/Stac/StacRouter.cs	74.02% <60.00%> (-1.32%)	⬇️
.../Translators/StacCollectionToAtomItemTranslator.cs	88.63% <66.66%> (-1.61%)	⬇️