feat: build icrc1_transfer consent message if target does not implement ICRC-21

[peterpeterparker]

Motivation

We were requested to extend the library to build ICRC-21 pseudo content message for icrc1_transfer as if they were generated by a target canister because some ledgers and canisters might not have implemented those specifications.

Changes

• Add a constants to map the methods to the custom builder. Currently only icrc1_transfer.
• Implement logic in service:
  • If call consent message fails
  • Check if there is a mapping for the method with a builder
  • If yes, fetch the token metadata
  • Finally build the markdown as it was a consent info response