Stunner - Line splicing

The goal for this task is to be able to perform line splicing.

Line splicing is a feature that allows dropping a shape on top of a connector (eg: line) in order to automatically split it into two connetors and perform the right connection assignments.

For example, consider the following BPMN flow:

• * T1 and T2 are tasks
• C1 is a sequence flow

At that point, once line splicing is working, creating a new task T3 and moving it on top of C1 will result as:

NOTE: The line splicing is already available on lienzo side, it's missing the Stunner integration for it - commands, rules, etc

Acceptance criteria

If two nodes are connected with sequence flow and the third one is dragged and dropped over this sequence flow, a new one sequence flow is created:

• If the connection is allowed the connector is highlighted in blue when the node is being dragged over the connector.
• Target of the initial sequence flow changes to a new ("dropped") node
• The new sequence flow has the Source set to the new node and the Target of this flow is set to the Target of the initial sequence flow.
• The new node is placed at the position it was dropped.
• If the line splice is being performed in a container such as a lane, the containment operation has to be performed as well.
• Undo and Redo operations are suported.
• Line splice must be compliant to all allow node connection rules.

Other cases:

• If the connection is not allowed the connector is highlighted in red when the node is being dragged over the connector.
• In case there is no enough space to splice the initial sequence flow, the line splice isn't performed. 

Scope

• This new feature will be available on all kogito channels (vscode, standalone, online, etc)
• BPMN and DMN editors
• BC editors are out from scope