The data for the boundary:

boundary_type - It indicates whether the boundary is open or closed.
It is not used when the boundaries are created from
a face. Boundaries created from a face are always closed.
plane_type - It indicates whether the plane of the boundary is
defined by the user or defined automatically.
It is not used when the boundaries are created from
a face. Boundaries created from a face are always automatic.
origin - It is the origin of the plane.
It is used only if the plane type is user defined.
matrix - It is the rotation matrix of the plane.
It is used only if the plane type is user defined.
material_side - It indicates the material side of the boundary.
ignore_holes - It indicates whether the boundaries are to be created
from the holes in the face, or if the holes are to be ignored.
ignore_islands - It indicates whether the boundaries are to be created
from the islands in the face, or if the islands are to be ignored.
ignore_chamfers - It indicates whether or not to ignore the chamfers and blends
of the face. Boundaries will be extended to the chamfers and blends
of the face if this value is set to one.
app_data - It is the application data applied to the boundary.
Set it to NULL if the boundary has no application data.