user should see informative error messages for BAD REQUEST in Merchants

when user enters bad info in the UI (before deployment is requested), error comes back BAD REQUEST (e.g. merchant ID is duplicated, phone number doesn't meet requirements, etc.)

although the field is highlighted in red, we should change text to be more informative. If cannot be very specific, then at least say, "Please review the online help to make sure the information entered meets the requirements and does not have any restricted characters."