Add support for environments

[alson]

Environments are a feature in Github that allows setting up deployment rules, like manual approval, per repository. Because they can only be configured per repository, this makes automating their management particularly important for many-repository micro-service application. This PR adds support for getting, creating, updating and deleting environments as documented here.

This partially implements the features requested by issue 2067 (environments, but not environment secrets).

[alson]

The linter CI run failed, but the failure is that git is prompting for credentials to clone some packages from Gitlab. So that does not look related to my changes in any way, since I didn't touch the build or requirements files. Locally I get the same error with PyGithub:master.

[willejs]

I would love to see this merged somehow!

[codecov-commenter]

Codecov Report

Patch coverage: 97.93% and project coverage change: -0.01 ⚠️

Comparison is base (7be3f76) 98.49% compared to head (0f68d01) 98.48%.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2223      +/-   ##
==========================================
- Coverage   98.49%   98.48%   -0.01%     
==========================================
  Files         124      128       +4     
  Lines       12418    12612     +194     
==========================================
+ Hits        12231    12421     +190     
- Misses        187      191       +4     

Impacted Files	Coverage Δ
github/EnvironmentDeploymentBranchPolicy.py	96.29% <96.29%> (ø)
github/EnvironmentProtectionRuleReviewer.py	96.96% <96.96%> (ø)
github/EnvironmentProtectionRule.py	97.36% <97.36%> (ø)
github/Environment.py	98.63% <98.63%> (ø)
github/Repository.py	97.13% <100.00%> (+0.03%)	⬆️

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[Paul-AUB]

Same, I'm very interested in this feature !

[EnricoMi]

Looks good.

We are migrating away from .pyi files. Can you please merge all typing information from new .pyi files (so not Repository.pyi) into the corresponding .py files? This will help not building up tech debt.

[alson]

@EnricoMi Thanks for your review! I merged the types into the .py files for the new files I created.

[EnricoMi]

LGTM!