build improvements

[philvarner]

Numerous build improvements:

• add 3.9 and 3.10 to the text matrix
• update black, isort, and flake8 versions
• add instructions to install pre-commit hooks and how to run tox
• remove all unused imports
• change line length to 120 b/c there are a lot that are longer than 90
• fixup warnings from flake8
• not sure why numpy was a dep for running tox?
• add config for running mypy, but leave commented since there are a number of problems to fix

[kylebarron]

Regardless of the value here, black defaults to 88, so they suggest setting the flake8 config to 88: https://black.readthedocs.io/en/stable/the_black_code_style/current_style.html#line-length

[philvarner]

I was wondering about that -- black wasn't giving an error but flake8 was on those lines. I've updated the flake8 config per the black documentation.

[codecov-commenter]

Codecov Report

Merging #109 (7e62410) into master (88bac55) will increase coverage by 0.55%.
The diff coverage is 98.92%.

@@            Coverage Diff             @@
##           master     #109      +/-   ##
==========================================
+ Coverage   96.27%   96.82%   +0.55%     
==========================================
  Files          20       20              
  Lines         483      473      -10     
==========================================
- Hits          465      458       -7     
+ Misses         18       15       -3     

Flag	Coverage Δ
unittests	96.82% <98.92%> (+0.55%)	⬆️

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

Impacted Files	Coverage Δ
stac_pydantic/__init__.py	100.00% <ø> (ø)
stac_pydantic/api/__init__.py	100.00% <ø> (ø)
stac_pydantic/api/search.py	96.25% <94.11%> (+0.04%)	⬆️
stac_pydantic/api/collections.py	90.90% <100.00%> (ø)
stac_pydantic/api/extensions/context.py	100.00% <100.00%> (ø)
stac_pydantic/api/extensions/fields.py	91.30% <100.00%> (ø)
stac_pydantic/api/extensions/sort.py	100.00% <100.00%> (ø)
stac_pydantic/api/landing.py	100.00% <100.00%> (ø)
stac_pydantic/api/utils/link_factory.py	100.00% <100.00%> (ø)
stac_pydantic/catalog.py	100.00% <100.00%> (ø)
... and 7 more

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[moradology]

Is this meant to be commented out?

[moradology]

Feel free to disregard: just saw that this has an answer in the PR description

[moradology]

For some reason pre-commit gave me some more type issues than my local mypy run... I should have this polished up later tonight or tomorrow morning

[geospatial-jeff]

The build changes look good to me, although there are other breaking changes sprinkled through the PR (like removing of Link.__iter__) and several others which means we will have to release as a new major version.

I think I would like to separate the build improvements from the functionality change to isolate the breaking code changes in a different PR.

[moradology]

Yeah, I think you make a totally valid point. A bit of context on the breaking changes: the shift from Link.__iter__ to Link.link_iterator is explicitly to avoid breaking a substitution rule which mypy enforces. In general, where breaking changes happened, it was in attempting to fix the numerous mypy errors. Is the preferred approach to remove such changes and sprinkle in # type: ignores?

[moradology]

After further discussion, it looks like the most sensible move might be to accept this PR after cutting a minor release. This will avoid the complexities of getting this PR's non-breaking bits in without the breaking portions.