As a developer integrating Pillarbox I find it misleading to be able to set any Commanders Act source key while not being able to set an associated site id.

As a Pillarbox developer I want to make our APIs easier to use and understand, while avoiding incorrect usage.

Hints

• Site id and source key are related.
• The unique source id supported by Pillarbox is 3666 (GD). This site id has only two valid associated source keys.

Acceptance criteria

• Only valid supported source keys for site id 3666 are possible.

Tasks

• Replace source key constants with an enum.
• Update documentation.