Verify requests with REQUESTS_CA_BUNDLE if set

[thwllms]

Related Issue(s):

• Respect REQUESTS_CA_BUNDLE environment variable #664

Description: By default, the basic requests.get, requests.post, etc., functions look for an environment variable REQUESTS_CA_BUNDLE (see docs), which can point to a custom certificate bundle file instead of the default bundle provided with certifi. This is common practice in e.g., corporate settings where HTTPS inspection is being performed with SSL certificate replacement, causing HTTPS responses with odd-looking certificates. This PR ensures that pystac-client also respects the REQUESTS_CA_BUNDLE environment variable.

PR Checklist:

• Code is formatted
• Tests pass
• Changes are added to the CHANGELOG

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 93.68%. Comparing base (21435b0) to head (c1a234c).
Report is 20 commits behind head on main.

Files	Patch %	Lines
pystac_client/stac_api_io.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #665      +/-   ##
==========================================
+ Coverage   93.43%   93.68%   +0.24%     
==========================================
  Files          13       13              
  Lines         990      997       +7     
==========================================
+ Hits          925      934       +9     
+ Misses         65       63       -2     

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[thwllms]

Updated to include fallback to CURL_CA_BUNDLE if REQUESTS_CA_BUNDLE isn't set, following the pattern in requests.
https://github.com/psf/requests/blob/2a438c27b5a5828c8ea0dc958112eecffca70b12/src/requests/sessions.py#L767

[gadomski]

@thwllms thanks for the PR! When reviewing, it felt like we should try to use requests's environment lookup if possible. I've opened #669 with an alternate solution, let me know what you think.

[thwllms]

@thwllms thanks for the PR! When reviewing, it felt like we should try to use requests's environment lookup if possible. I've opened #669 with an alternate solution, let me know what you think.

Ah, I totally missed merge_environment_settings when I was going through the docs! I like that solution better. 👍

[thwllms]

Closing in favor of #669