feat: add HELM_S3_DYNAMIC_REGION flag to disable dynamic region discovery

[sasanyasari]

Overview

Add support for disabling dynamic bucket region detection via the HELM_S3_DYNAMIC_REGION environment variable.

Problem

The current implementation of DynamicBucketRegion always performs automatic bucket region detection by making HEAD requests to Amazon S3, which causes several issues:

1. Breaks plugin in restricted environments: Environments with limited internet access or strict egress filtering cannot make the required HEAD requests to s3.amazonaws.com
2. Security/privacy concerns: Internal bucket names are leaked to Amazon S3 even when using alternative S3-compatible storage solutions
3. Ignores user configuration: The HEAD requests always go to Amazon S3 (s3.amazonaws.com) regardless of custom endpoints configured via AWS_ENDPOINT or AWS profiles

Solution

Introduce HELM_S3_DYNAMIC_REGION environment variable:

• Default: true (enabled) - maintains backward compatibility
• Set to false: Disables dynamic region detection, relies on standard AWS region configuration

Usage

To disable dynamic bucket region detection:

export HELM_S3_DYNAMIC_REGION=false

This is particularly useful for:

• Environments with restricted internet access
• Alternative S3-compatible storage (MinIO, Ceph, etc.)
• Security-sensitive environments where bucket names should not be exposed to AWS
• CI/CD pipelines requiring predictable region behavior

Testing

All existing tests pass, and new tests verify.

Backward Compatibility

✅ Fully backward compatible - existing users will see no change in behavior unless they explicitly set HELM_S3_DYNAMIC_REGION=false.

Fixes #220

[zibarev]

Thanks for the PR — this addresses a real pain point.

[hypnoglow]

Thank you!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.16%. Comparing base (8bd4713) to head (676378f).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #599      +/-   ##
==========================================
+ Coverage   69.11%   69.16%   +0.05%     
==========================================
  Files          32       32              
  Lines        1185     1187       +2     
==========================================
+ Hits          819      821       +2     
  Misses        366      366              

Flag	Coverage Δ
e2e	67.56% <50.00%> (-0.03%)	⬇️
unit	14.99% <100.00%> (+0.14%)	⬆️

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