test(): Add comprehensive unit tests for values.go functions

[Arpit529Srivastava]

Description

This PR introduces unit tests for the MergeMaps and GenerateValuesFile functions in pkg/internal/values.go, which handle YAML map merging and Helm values file generation. Both functions have been exported and updated throughout the codebase for improved testability.

Two bugs were fixed: handling of nil maps in MergeMaps, and correcting the merge order in GenerateValuesFile so user values override defaults. The test suite now covers 19 scenarios, including merges, nested maps, empty and nil inputs, error cases, and real-world HelmChart configs. All tests pass and existing functionality is unchanged.

This is under #46 issue

How Has This Been Tested?

• MergeMaps function with 9 test cases (simple merge, nested merge, nil maps, etc.)
• GenerateValuesFile function with 7 test cases (basic generation, complex nested values, error handling)
• Real-world HelmChart configuration testing
• Error condition testing (invalid file paths, nil inputs)
• Verified all existing functionality still works with go build and go test

Checklist:

• The title of the PR states what changed and the related issues number (used for the release note).
• Does this PR requires documentation updates?
• I've updated documentation as required by this PR.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have tested it for all user roles.
• I have added all the required unit test cases.

Does this PR introduce a breaking change?

No breaking changes. Functions are now exported but maintain the same interface and behavior.

N/A

[Arpit529Srivastava]

PTAL @narmidm @Rahul-D78 @gourishkb
Thank you