Redesign DB layout for shapes

[nmanovic]

Need to improve layout of our database. Better to have only one Shape class instead of BoundingBox, Polygon, Polyline, Points. Probably it will simplify our code.

class ShapeType(str, Enum):
    RECTANGLE = 'rectangle'
    POLYGON = 'polygon'
    POLYLINE = 'polyline'
    POINTS = 'points'

    @classmethod
    def choices(self):
        return tuple((x.name, x.value) for x in self)

class Annotation(models.Model):
    job   = models.ForeignKey(Job, on_delete=models.CASCADE)
    label = models.ForeignKey(Label, on_delete=models.CASCADE)
    frame = models.PositiveIntegerField()
    group_id = models.PositiveIntegerField(default=0)
    client_id = models.BigIntegerField(default=-1)

    class Meta:
        abstract = True

class Shape(models.Model):
    id = models.BigAutoField(primary_key=True)
    type = models.CharField(max_length=16, choices=ShapeType.choices())
    occluded = models.BooleanField(default=False)
    z_order = models.IntegerField(default=0)
    points = models.TextField()

    class Meta:
        default_permissions = ()

class LabeledImage(Annotation):
    pass

class LabeledImageAttributeVal(AttributeVal):
    image = models.ForeignKey(LabeledImage, on_delete=models.CASCADE)

class LabeledShape(Annotation, Shape):
    pass

class LabeledShapeAttributeVal(AttributeVal):
    shape = models.ForeignKey(LabeledShape, on_delete=models.CASCADE)

class ObjectTrack(Annotation):
    id = models.BigAutoField(primary_key=True)

class ObjectPathAttributeVal(AttributeVal):
    track = models.ForeignKey(ObjectTrack, on_delete=models.CASCADE)

class TrackedShape(Shape):
    track = models.ForeignKey(ObjectTrack, on_delete=models.CASCADE)
    frame = models.PositiveIntegerField()
    outside = models.BooleanField(default=False)

    class Meta:
        default_permissions = ()

class TrackedShapeAttributeVal(AttributeVal):
    shape = models.ForeignKey(TrackedShape, on_delete=models.CASCADE)