refactor: eliminate hidden mutations in HelmRepository client opts

[cappyzawa]

Summary

Refactors HelmRepository client options generation to use explicit configuration pattern. The previous implementation had hidden mutable side effects where ClientOpts was modified through configuration functions, making the code harder to reason about.

Changes

• Replace hidden mutation functions with explicit configuration pattern
• Add CertsTempDir field to ClientOpts and update GetClientOpts signature to return (*ClientOpts, error) instead of (*ClientOpts, string, error)
  • Update all callers to use clientOpts.CertsTempDir
• Improve error messages to include namespace/name for better debugging

Related

Addresses similar error message clarity issues identified in #1852 (comment)

[stefanprodan]

@cappyzawa can you please rebase and solve conflicts, would be great to get this merged.

[cappyzawa]

Previously, I discussed refactoring with @matheuscscp once helm/helm#31076 was merged and available, but I forgot to mention it here—sorry about that.

Since it looks like helm/helm#31076 is still planned only for Helm 4 and there haven’t been any updates, I suppose any improvements to this PR will have to wait until then.

[matheuscscp]

Yeah I think we can wait until we can remove this tmp dir altogether to merge this one

[matheuscscp]

@cappyzawa The initial (and probably most substantial) Helm 4 PR has been merged:

#1953

Feel free to check if this one is still relevant 👌

[cappyzawa]

Thanks for the ping @matheuscscp!

I checked how the Helm 4 migration addressed the issues this PR was trying to solve:

Goal	Status
Eliminate hidden mutations	✅ Solved - main now uses explicit argument passing (configureAuthentication(opts *ClientOpts)) instead of the functional option pattern
Add CertsTempDir to ClientOpts	✅ No longer needed - Helm 4's LoginOptTLSClientConfigFromConfig(*tls.Config) allows passing TLS config in memory, so temp files are gone entirely
Improve error messages with namespace/name	Partially addressed in main

Since the Helm 4 + ORAS v2 migration solved these issues with a cleaner architecture, I'll close this PR.