Editing Grease Pencil Strokes Using Curves

Since the Blender 2.8 update, that introduced the Grease Pencil object type, there are a couple of primitives that can be added in the Grease Pencil draw mode. The user can draw a shape (e.g. a circle, arc, rectangle, etc.) using the respective tool, edit it and confirm the creation of the stroke. After this step, the shape can no longer be manipulated as a curve. I propose to add an interactive edit mode tool, that allows the user to manipulate any Grease Pencil stroke using curve handles.