Implement Junction Finder

[gfontorbe]

Solves #420

Adds a new feature to find junction points on edges with the same source or target.

Similar to the IntersectionFinder, we provide a ContainerModule that can be loaded when needed in the inversify container.

The JunctionFinder ultimately sets the isJunction flag to true on RoutingPoints where a junction point must be drawn.

The rendering is done in the PolylineEdgeView (and therefore views that inherit this view) in a new function renderFunctionPoints.

They are represented as circles with a class sprotty-junction for easy styling.

[spoenemann]

Thanks!

In which example have you tested the new feature? Maybe we can extend the "Random Graph" example so that some edges are randomly assigned to the same port?

[gfontorbe]

In which example have you tested the new feature? Maybe we can extend the "Random Graph" example so that some edges are randomly assigned to the same port?

I modified the random graph example to fit my needs, I could probably find time to work on modifying the example to include optional junction points

[spoenemann]

I'm seeing strange spider webs when I enable port merging:

Do you know what's going on? Is it an issue in the example or in ELK?

[gfontorbe]

I'm seeing strange spider webs when I enable port merging:

Do you know what's going on? Is it an issue in the example or in ELK?

That's the same issue that has been reported in #427.

Bend points are not removed so you end up with funky edges. Usually happens when you show/hide junction points several times without reloading the page. First render seems to work fine most of the time on my end.

[spoenemann]

👍