Flowable editor - Support for tirggerable correlation, channel and event keys

[maratkalibek]

Is your feature request related to a problem? Please describe.

Flowable BPMN xml file also supports following elements:

• <flowable:channelKey>...</flowable:channelKey>
• <flowable:triggerEventCorrelationParameter name="correlationId" type="string" value="${correlationId}"/>
• <flowable:triggerEventType>...</flowable:triggerEventType>
• <flowable:triggerChannelKey>...</flowable:triggerChannelKey>

Describe the solution you'd like

Support to be added to the modeler

Describe alternatives you've considered
Flowable UI editor from flowable-6.8.0 have these options

Additional context

        <serviceTask id="theTask1"
                     name="my task"
                     flowable:triggerable="true"
                     flowable:type="send-event">
            <extensionElements>
                <flowable:channelKey>outChannel1</flowable:channelKey>
                <flowable:eventType>outEvent1</flowable:eventType>
                <flowable:eventInParameter xmlns:flowable="http://flowable.org/bpmn"
                                           source="customerName"
                                           sourceType="string"
                                           target="eventVar1"/>
                <flowable:eventInParameter xmlns:flowable="http://flowable.org/bpmn"
                                           source="correlation-123"
                                           sourceType="string"
                                           target="correlationId"/>
                <flowable:triggerEventCorrelationParameter xmlns:flowable="http://flowable.org/bpmn"
                                           name="correlationId"
                                           type="string"
                                           value="#{java.util.UUID.randomUUID()}"/>
                <flowable:triggerEventType>inEvent1</flowable:triggerEventType>
                <flowable:triggerChannelKey xmlns:flowable="http://flowable.org/bpmn">inChannel1</flowable:triggerChannelKey>
            </extensionElements>
        </serviceTask>