[Transfer App] Return Result instead of boolean for is_send_enabled and is_receive_enabled‍‍ methods

[Farhad-Shabani]

Problem Definition

The is_send_enabled and is_receive_enabled methods under the TokenTransferValidationContext return a boolean value whose sole purpose is to propagate errors. This violates Rust's error-handling convention of using the Result type for error reporting.
This implementation was suitable as long as no specific error reporting was required, but it can become an issue as our codebase grow and require more detailed error reporting.

[plafer]

whose sole purpose is to propagate errors.

can you expand on that? IMO, the purpose is to fail the transfer if for any reason the hosts wants to freeze transfers. In other words, it's sort of a "kill switch" on transfers.

[Farhad-Shabani]

can you expand on that? IMO, the purpose is to fail the transfer if for any reason the hosts want to freeze transfers. In other words, it's sort of a "kill switch" on transfers.

Indeed, it is. What I meant:

• It's actually uncommon to use a boolean as a return type instead of Result to handle failures. In our case, we return a boolean and just afterward use it to handle failures. Why not just fail right away?
• Also, this way implementors have more control over the message of propagated error and can keep it consistent with their own project