﻿Write a SpacetimeDB backend module in Rust that defines a new sum type and uses it in a table.

TYPES
- Struct: Rect
  - Fields:
    - width: i32
    - height: i32
- Enum: Shape
  - Variants:
    - Circle(i32)
    - Rectangle(Rect)

TABLE
- result
  - Struct: ResultRow
  - Fields:
    - id: i32 (primary key)
    - value: Shape

REDUCERS
- set_circle: given id:i32 and radius:i32, insert exactly one row into result
  - (id=id, value=Shape::Circle(radius))
