Function insert_props 

pub async fn insert_props(
    conn: &mut AsyncPgConnection,
    props: &DrawingVariantEntity,
) -> QueryResult<()>

Insert properties for a newly created drawing.

Depending on the variant (Rectangle, Ellipse, LabelText, etc.), this inserts into the appropriate *_props table.

For complex shapes (FreeLine and BezierPolygon), this will:

• Insert the props record into the main props table
• Insert all associated point rows into the corresponding *_point table

Errors

• If p.drawing_id does not reference an existing drawing (FK violation)
• If required fields in the props struct are missing or violate constraints