fix: Improve merge logic for parameterSecretRefs and parameters

[jn-av]

📝 Description

Currently, the merge between parameterSecretRefs and parameters happens at a high level.
Since both objects contain a data field directly underneath, the values of these fields are simply overwritten rather than merged.

This leads to cases where a single field (for example, adminPassword) overwrites the entire data object, which is unintended and causes loss of existing values.

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💡 Proposed Change

Implement a recursive (deep) merge for these objects to ensure that:

• Only explicitly provided fields are updated.
• Existing data remains intact and is not overwritten unintentionally.

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✅ Benefits

• Prevents accidental data loss when merging.
• Ensures expected behavior when both parameters and parameterSecretRefs define overlapping keys.
• Improves reliability and maintainability of parameter handling.

[sdischer-sap]

@jn-av looks already promising ;) Let us know when its ready for review.

[enrico-kaack-comp]

The logic looks great.
This is a single functions without dependencies, would be also a perfect opportunity to test this function itself without the ComplexParameterJson context.

This way it would also be easily visible what this function is expected to do, sort of usage example :)

[SatabdiG]

Excellent fix 🚀 with great test coverage. Good work!!

[sdischer-sap]

Can only agree, great work!