Raise exception when extending object that does not have schema URI

[duckontheweb]

Related Issue(s):

• Raise exception on attempt to extend object not implementing that extension #370

Description:

Introduces a new ExceptionNotImplemented exception type and raises this when attempting to extend an object that does not include that extension's schema URI in stac_extensions. See the corresponding issue for discussion of how Assets without an owner are handled.

Also adds an add_if_missing boolean option to the *Extension.ext methods that will add the schema URI to the object's stac_extension list if it is missing (see this PR comment for original suggestion).

PR Checklist:

• Code is formatted (run pre-commit run --all-files)
• Tests pass (run scripts/test)
• This PR maintains or improves overall codebase code coverage.
• Changes are added to the CHANGELOG. See the docs for information about adding to the changelog.

[codecov-commenter]

Codecov Report

Merging #450 (5f2296f) into main (7f8e7aa) will increase coverage by 0.51%.
The diff coverage is 93.12%.

@@            Coverage Diff             @@
##             main     #450      +/-   ##
==========================================
+ Coverage   90.80%   91.31%   +0.51%     
==========================================
  Files          40       40              
  Lines        5120     5204      +84     
==========================================
+ Hits         4649     4752     +103     
+ Misses        471      452      -19     

Impacted Files	Coverage Δ
pystac/__init__.py	100.00% <ø> (ø)
pystac/extensions/item_assets.py	65.85% <16.66%> (-3.38%)	⬇️
pystac/extensions/datacube.py	62.26% <72.72%> (+5.23%)	⬆️
pystac/extensions/raster.py	90.61% <94.44%> (+0.39%)	⬆️
pystac/errors.py	88.88% <100.00%> (+0.65%)	⬆️
pystac/extensions/base.py	92.45% <100.00%> (+0.78%)	⬆️
pystac/extensions/eo.py	96.69% <100.00%> (+0.09%)	⬆️
pystac/extensions/file.py	95.38% <100.00%> (+0.18%)	⬆️
pystac/extensions/label.py	96.51% <100.00%> (+0.06%)	⬆️
pystac/extensions/pointcloud.py	96.69% <100.00%> (+0.08%)	⬆️
... and 10 more

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[duckontheweb]

@gadomski @lossyrob Would be good to get your feedback on this draft implementation on the EO extension before I start implementing it on the other extensions.

[lossyrob]

Seems straightforward to me, +1

[gadomski]

LGTM

[duckontheweb]

@gadomski @lossyrob This is ready for final review. I also added the add_if_missing argument suggested here

[gadomski]

LGTM. Thanks for taking this on, that is a lot of boilerplate to churn through 🙇🏽.

[lossyrob]

🚀

[duckontheweb]

LGTM. Thanks for taking this on, that is a lot of boilerplate to churn through 🙇🏽.

Yeah, it would be good to look at this at some point to see if we can reduce any of this through inheritance, but I didn't see any easy way here.