I can add a payload mapping to a sequence flow

[ThorbenLindhauer]

For sequence flows leading to a parallel gateway, users can define a payload mapping. The purpose is to merge the payloads of the branches into one in a predictable fashion. This mapping is an extension elemement of the sequence flow.

Example:

<sequenceFlow id="flow" sourceRef="task" targetRef="join">
  <extensionElements>
    <zeebe:payloadMappings>
      <zeebe:mapping source="$.key1" target="$.mappedKey1" type="PUT"/>
      <zeebe:mapping source="$.key2" target="$.mappedKey2" type="COLLECT"/>
    </zeebe:payloadMappings>
  </extensionElements>
</sequenceFlow>

source and target can contain any String. type is an enum with values PUT and COLLECT. PUT should be the default.

[dominikhorn93]

Done with release 0.2.0