Feature request: data field on token mint and melt

[obiyankenobi]

We need to allow use cases to send a data field to mint and melt endpoints. Ideally, the data field should be the first output. This is similar to the data field on the token creation.

[msbrogli]

Why don't we create a /create-tx endpoint that is flexible enough to create any transaction? It would allow users to pass multiple inputs and outputs, and some of them would have markers that would be filled by the wallet (e.g., change address). It might also have parameters such as "shuffle outputs".