feat: expose response headers in InfluxDBError

[karel-rehor]

Proposed Changes

• add helper method to get response headers in InfluxDBError
• add tests of this new functionality
• in examples add config.py with Config class to centralize resolution of environment variables usable in examples
• fix cloud_dedicated_write.py which used outdated import of write_options
• add example of working with response header values on write

Checklist

• CHANGELOG.md updated
• Rebased/mergeable
• A test has been added if appropriate
• Tests pass
• Commit messages are conventional
• Sign CLA (if not already signed)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 55.12%. Comparing base (0925d5c) to head (66ae494).
Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
+ Coverage   55.08%   55.12%   +0.04%     
==========================================
  Files          33       33              
  Lines        2046     2048       +2     
==========================================
+ Hits         1127     1129       +2     
  Misses        919      919              

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[bednar]

LGTM 🚀