refactor: remove IssuerTransfer choice from NativeTokenConfig

[salindne]

Summary

Remove the IssuerTransfer choice from NativeTokenConfig as it's no longer needed with the custodial key model.

Why

With the custodial key model implemented in canton-middleware:

• The API server now manages Canton signing keys for users
• Transfers use the standard CIP56Holding.Transfer choice (owner-controlled)
• The API server signs transactions as the user's Canton party
• Issuer-mediated transfers are no longer necessary

Related

• canton-middleware PR: feat: Custodial key management for Canton user registration canton-middleware#53

[gemini-code-assist]

Summary of Changes

Hello @salindne, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request refactors the NativeTokenConfig by eliminating the IssuerTransfer choice. This modification is essential to align the system with the newly implemented custodial key model, where the API server handles user Canton signing keys and all token transfers are processed through the standard owner-controlled CIP56Holding.Transfer mechanism, simplifying the token transfer process and removing redundant functionality.

Highlights

• Removal of IssuerTransfer Choice: The IssuerTransfer nonconsuming choice has been removed from the NativeTokenConfig template.
• Alignment with Custodial Key Model: This change aligns the token configuration with the new custodial key model, where the API server manages Canton signing keys for users.
• Standardized Transfers: Token transfers now exclusively utilize the standard CIP56Holding.Transfer choice, which is owner-controlled, making issuer-mediated transfers obsolete.

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[gemini-code-assist]

Code Review

This pull request correctly removes the IssuerTransfer choice from NativeTokenConfig, which is a good simplification to align with the new custodial key model. My review includes a comment on the introduced changes, highlighting that related code, such as a test case and an event template, now needs to be removed to ensure the codebase remains consistent and the test suite passes.

[kalambet]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a clean and logical refactoring by removing the IssuerTransfer choice from NativeTokenConfig, along with its associated TransferEvent template and test script. The justification for this change, moving to a custodial key model where owner-controlled transfers are used, is sound. The removals are consistent across the affected files, leading to a simpler and more maintainable codebase. The changes are correct and I have no suggestions for improvement.