feat: update S3 client initialization for retriever and exporter

[hoangnv-bkhn]

Description

• Problem:
  When the S3 client is initialized for retrievers and exporters, the application does not allow the user to further configure how the S3 client should behave. (It currently only accepts AwsConfig as a parameter).
• The way it was resolved:
  Add an optional field to the Retriever/Exporter structure
  Use this field when initializing the S3 client
• How to test the change:
  Refer to the options that AWS allows to configure here and implement the appropriate custom functions.

Closes issue(s)

Resolve #2451

Checklist

• I have tested this code
• I have added unit test to cover this code
• I have updated the documentation (README.md and /website/docs)
• I have followed the contributing guide

[netlify]

✅ Deploy Preview for go-feature-flag-doc-preview canceled.

Name	Link
🔨 Latest commit	22274d4
🔍 Latest deploy log	https://app.netlify.com/sites/go-feature-flag-doc-preview/deploys/67067ec899143000099f028d

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.18%. Comparing base (012659f) to head (22274d4).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2480   +/-   ##
=======================================
  Coverage   86.18%   86.18%           
=======================================
  Files         100      100           
  Lines        3526     3526           
=======================================
  Hits         3039     3039           
  Misses        360      360           
  Partials      127      127           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[thomaspoignant]

Thanks for this addition, this is really great to have a more extensible s3 integration.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud