Button to create new related pub on pub details page

[gabestein]

Motivation

So users can create related pubs the way they can create children

So Unjournal can continue to use their process

Requirements

• Adds a "Create Related Pub" button below the "Related Pubs" header, just like the current "Add new pub" button
• In popup, adds a field to select a relationship type that allows user to select from relationship fields on the "from" pub type
• In popup, render interface for adding the value of the the relationship, same as current value UI.
• When new pub is created, it should be added as a relation to the "parent" pub

Acceptance Criteria

• Reuses "add related" design from forms to add relationship value in popup

Extra work

Mockups (if available)

[allisonking]

should this also consider the "value" of the relationship, or just leave null?

[gabestein]

Right. Woof. I think for now leaving null is fine. Then maybe we could add it to...the form that loads, right?

[gabestein]

Actually, more I think about it, more I think we should render a field for it if it's not null...