latest updates:

• we decided to pause the support for body_as_str method until there're customer requests.
• The ServiceBusMessage (and other message model) should implement the repr method as per our guideline here: https://azure.github.io/azure-sdk/python_design.html#python-models-repr

right now, msg.body returns a generator since it's directly returning the data object from the uamqp message object.

It means to extract contents as a string I have to do next(msg..body).decode('utf-8')

body_as_Str would be a nice convenience to add ; there's on in EH too