UTF8 strings instead of Base64 bytes for InternalizeAction prefix/suffix

[jchavannes]

Description of Changes

Provide a brief description of the changes you've made.

Linked Issues / Tickets

Reference any related issues or tickets, e.g. "Closes #123".

Testing Procedure

Describe the tests you've added or any testing steps you've taken.

• I have added new unit tests
• All tests pass locally
• I have tested manually in my local environment

Checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have updated CHANGELOG.md with my changes
• I have run npm run doc and npm run lint one final time before requesting a review
• I have fixed all linter errors to ensure these changes are compliant with ts-standard
• I have run npm version patch so that my changes will trigger a new version to be released when they are merged

[BraydenLangley]

Why are we changing derivation prefix/suffix to utf8 vs. base64?

[sonarqubecloud]

Quality Gate failed

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D Maintainability Rating on New Code (required ≥ A)

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[ty-everett]

Is this PR still active? None of the checklist items have been completed, and no justification has been given for changing the key derivation. This would be a breaking change with wide-ranging consequences, including changes that impact the behavior of BRC-100 wallets. Unless a compelling justification can be offered, I wouldn't support this breaking change.

[chris-4chain]

I think it might be based on my recent suggestion, so I'd like to offer a bit of clarification. 😅
My intention was not to change the TypeScript version, as that could be an unnecessary breaking change.

My suggestion was to change the DerivationPrefix and DerivationSuffix types from []byte to string only in the Go SDK.

Here's my reasoning:

1. Consistency with TypeScript - The TS implementation sends the Base64 value over the wire as a string. When this is received on the Go side as a []byte, it causes confusion. We've seen several developers struggle with how to handle this byte slice correctly.
2. Internally, services like wallet-toolbox-wallet already send these prefixes as a string to wallet-toolbox-storage via JsonRPC. The current []byte type forces us to constantly convert from string to []byte and back again.
3. The documentation and the TS SDK already use strings. Since the keyID is a string (e.g., "prefix suffix"), using []byte for its components is confusing for new developers. It leads to questions like, "What format should I use here? []byte(derivationPrefix) or Base64Encode(derivationPrefix)?" Using string makes the expected input much clearer.

So, the discussion (in my perspective) concerns only the golang version.

[jchavannes]

@chris-4chain updating Golang breaks the wire serialization protocol with TypeScript. That is why changing Golang requires TypeScript change.