How to create custom shapes with custom connection points for DiagramDesignerControl

The Diagram control supports a special language for defining shapes. The main element that contains shape description is ShapeTemplate. This element describes a shape contour and may contain several segments:
- Start. Specifies the start point
- Line. Defines a line with start and end points
- Arc. Defines an arc with start and end points

To specify connection points, use the ShapeTemplate.ConnectionPoints property.
Shapes may contain parameters. Parameters may be used to dynamically calculate an end point, row height and other properties. To specify parameters, use the ShapeTemplate.Parameters property.
To register custom shapes, use the DiagramToolboxRegistrator.RegisterShapes method.