Create or update a custom UI extension

Create or update a UI extension to be managed through the Integrations Library. When creating an extension, its ID must be unique across all existing extensions, whether or not managed through the Integrations Library.
The following will cause an HTTP 409 Conflict response:

• No version is provided, and the provided ID exists;
• A version is provided, and the provided ID does not exist;
• A version is provided, but its value is not the latest.