Automatic end-to-end acknowledgement handling for connection sources and targets

[thjaeckle]

Building on the work on #611 the in Ditto managed connections shall automatically

• request acknowledgements when configured in sources
• delivering acknowledgements when configured in targets

Connection sources get an additional "required-acks" configuration.
Connection targets get an additional "delivered-acks" configuration.

For consuming messages via sources, the technical acknowledgement/settlement of the underlying protocols (AMQP 1.0, AMQP 0.9.1, MQTT 3, MQTT 5, Apache Kafka, HTTP) shall be applied accordingly:

• only technically ack/settle a message as "successfully processed" when all configured "required-acks" were successful
• either issue a technical nack or timeout for unsuccessful processings
• protocols shall redeliver the message when the message was sent with a certain QoS (e.g. "at least once")

For publishing messages via targets, wait for the technical confirmation of the client in order to automatically create an acknowledgement from it.
Reasonably fill the "status", "payload" and "headers" of the automatically created acknowledgement, e.g. for HTTP connections, the acknowledgement shall contain the HTTP status code as "status" and the response payload as "payload", also the HTTP response headers as "headers".