Versions

Every upload of a template creates a new version, numbered from 1. The rules:

• A new version arrives inactive. Uploading is not publishing: it goes live when someone presses Activate.
• Several versions can be active at the same time.
• A request that does not pin a version gets the highest active version number. Activating a newer version therefore rolls traffic forward with no change on the caller's side.
• A request pinning a version that is not active is refused, never silently served a different one. The error names the versions that are active, so a caller can recover.
• Deactivate template switches every version off at once and stops all generation for it. It asks for confirmation, and it is reversible: activate a version again afterwards.