Include recommended_min_amount_in in error if swap fails for insufficient fees

fishtail(9r)requested to merge
fishtail/recommended_min_amount_in_swap into develop

This MR close #2215 (closed). In the case the swap simulation fails due to ErrNotEnoughToPayFee, we include the recommended_min_amount_in in the message to inform the caller of the issue. The return code has also been changed to be 400 - Bad Request.

I would have liked to add this to the details portion of the response. Any thoughts/guidance on this would be appreciated.

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