Feat/set mint allowance for admin

[KristenPire]

Summary

This PR introduces the setMintAllowanceForAdmin function, allowing a system account to set the mint allowance for an admin account using a signature provided by an admin. This function is the sole change in this PR, along with corresponding tests to ensure 100% coverage.

This function's end goal is to allow the admin to authorize actions by simply signing a message rather than submitting a full transaction. This approach ensures that the system account is the sole payer for these transactions, centralizing fee management to a single account.

Details

• Functionality:

  • The setMintAllowanceForAdmin function enables a system account to raise the mint allowance on behalf of an admin, validated by a signature from the admin account.
  • The message to be signed by the admin is currently a static hash, allowing the function to confirm authorization based on this hardcoded message.
  • Only system accounts are permitted to call this function, and the admin providing the signature must be a recognized admin account.

• Tests:

  • 100% test coverage is provided for the setMintAllowanceForAdmin function.
  • Tests validate correct behaviour with valid signatures, rejection of invalid signatures and admin signatures are accepted.

Impact

This change is isolated to the setMintAllowanceForAdmin function and does not add additional dependencies or modify other functions.

Future Considerations

Depending on future design decisions, the hardcoded message may be replaced with a dynamic message to allow more flexibility in message signing.