fix: FileAuthProvider stores the same strategy for each entry

[mrschyte]

Proposed changes

This commit fixes a bug in the FileAuthProvider class when there are multiple secret entries. Currently the same pointer is used for creating the authentication strategy and thus a single credential (that was loaded last) will be tried for each domain.

Checklist

• Pull request is created against the dev branch
• All checks passed (lint, unit/integration/regression tests etc.) with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

[GeorginaReeder]

Thanks so much for your contribution @mrschyte !

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[tarunKoyalwar]

lgtm !

i thought this was fixed with recent go 1.22 but it seems like we are not using go 1.22 yet https://go.dev/blog/loopvar-preview. similar issues should be automatically resolves once we bump go mod version to 1.22