Reversed workflow for creating tickets and publications

To create a publication, we will first create a new content item using the `ContentAPI`. After a request has been sent to `/api/content/create`, the returned `contentId` needs to be used to create a new publication and ticket.

### Flow ###
1. Send request to `/api/content/create`
2. Pass the returned `contentId`, together with the publication metadata in the request to `/api/ticket/create`
3. When the `externalId` for the ticket is locked. we create a new publication.
4. When the publication has been created, we return the created ticket, decorated with the publication
How does this look like (in HTTP)? Do we post JSON to this endpoint?