Transaction simulation should return serialized `simulationResponse`

[aristidesstaffieri]

What problem does your feature solve?

Our simulation endpoints get the simulation response from RPC, then they prepare the transaction, then return the simulation response along with the prepared transaction to clients. This means that when the client side needs to use internal of the SimulateTransactionSuccessResponse like transactionData, they have no way to instantiate the associated class becuase we don't pass through the corresponding xdr.

What would you like to see?

Serialize the transactionData and return that along with the other SimulateTransactionSuccessResponse fields.

const data = {
  simulationResponse: {
    transactionData: simulationResponse.transactionData.build().toXDR(),
    .... the rest of the fields ....
 },
  preparedTransaction: built.toXDR(),
};

What alternatives are there?

Have clients reach into the transaction data internal fields for data that should be accessed through accesor methods.