#97 Creating a ticket dependency

Ticket deps are small objects just specifying a relationship. And it makes sense to me, that deps are essentially parts of the work that needs to be done on a work item, and a work item gets to control its list of dependencies. So, I'm inclined (both in spec and in Vervis) do ticket dependency creation using the `Offer` flow, without a `Create` flow. It's simpler and perhaps safer. If anyone has insights/thoughts/objections/arguments in favor of remotely-hosted ticket deps (i.e. a ticket's dependency objects can be hosted on other servers than the ticket itself), please comment in the forum thread linked below. For now, I'm going forward with the `Offer` flow. [Forum thread](https://talk.feneas.org/t/creating-a-ticket-dependency/301)