fix(argo-workflows): default S3 endpoint to s3.amazonaws.com when not set

[AndreKurait]

Fixes #3801

Summary

The S3 endpoint field in the artifact repository ConfigMap template renders an empty value when no endpoint is configured. The argoexec S3 driver passes this directly to minio-go (minio.New("")), which rejects it:

failed to create new S3 client: Endpoint:  does not follow ip address or domain name standards.

Neither an empty string nor omitting the key works — Go unmarshals a missing string field as "" (zero value), and argoexec has no empty-endpoint guard before calling minio.New(). The fix must provide a valid default.

Change

Default the endpoint to s3.amazonaws.com when not explicitly set:

Before:

endpoint: {{ tpl (.Values.artifactRepository.s3.endpoint | default "") . }}

After:

endpoint: {{ tpl (.Values.artifactRepository.s3.endpoint | default "s3.amazonaws.com") . }}

s3.amazonaws.com is the AWS global S3 endpoint. Minio-go explicitly recognizes it (IsAmazonEndpoint), enabling signature v4 and dual-stack automatically. It works with VPC gateway endpoints and interface endpoints (with private DNS enabled).

Deployments with custom endpoints (MinIO, LocalStack, GCS, etc.) are unaffected — their value takes precedence over the default.

Checklist:

• I have bumped the chart version according to versioning
• I have updated the documentation according to documentation
• I have updated the chart changelog with all the changes that come with this pull request according to changelog.
• Any new values are backwards compatible and/or have sensible default.
• I have signed off all my commits as required by DCO.
• I have created a separate pull request for each chart according to pull requests
• My build is green (troubleshooting builds).

[tico24]

You're the second person today who allowed their LLM to delete the PR checklist and to not do the things in them. Humans have to spend time reviewing these PRs.

Please mark this PR as draft, re add the checklist and follow it. Thank you.

[tico24]

https://github.com/argoproj/argoproj/blob/main/community/genai.md

[AndreKurait]

@tico24 Thank you, i'm ready for a re-review now with the checklist followed