AMQP 1.0 Output - Support for message body type

[timo102]

In AMQP 0.9 the message format was simple, and the message body was always an opaque byte array. In AMQP 1.0, the message body can be 1 of 3 types: data (opaque byte array), AMQP sequence (list of polymorphic data), or AMQP value (a single instance of polymorphic data). In the current implementation, the message is always sent as an opaque byte array. If the use case is to process JSON messages (UTF-8 String), then it is better to use AMQP as it was intended and send the data as AMQP value of type string. This increases compatibility and simplifies the usage of such a message.

My suggestion is to introduce an advanced configuration option called content_type. The allowed values are:

• opaque_binary: Same behavior as today. This is the default to keep compatibility and prevent a breaking change.
• string: New option which sends the message as string content.

The amqp_1 input module implementation already supports the string message type, so there is no change needed.

I will provide a pull request for this enhancement.