Support HTTP request for outbound mappings

[zhongys-c8y]

Now dynamic mapper support HTTP requests only for inbound mappings. If the dynamic mapper can send requests to another Microservice, the payload can be further processed.

[switschel]

Doable!
We might need to extend the existing Http Connector to be configured with a Base URL + Authentication.
When a outbound mapping is defined and a HTTP connector is selected the Base URL will be fetched and the mappings topic extended to it e.g. topic /measurements --> https://myOtherMicroservice/api/data/measurments. Payload will be the mapped payload.

Can we make the following assumptions?

• Can we assume that we always POST data or should we also allow PUT/PATCH methods?
• Can we assume that the content-type is always application/json for now? Could be a current limitation that it is only supported for JSON payloads, which makes it much easier for us.

[zhongys-c8y]

For the current use case(the payload needs to be decoded), I think POST is already sufficient. Application/json should be also fine.