Relationships and other reference fields

Post Object, Page Link, Relationship, Taxonomy and User fields show the same pickers in forms as on edit screens: search, pick, reorder.

#Searching

On edit screens pickers search through /cafe/v1/references, which is only open to people who edit content. In forms they search through the form's own endpoint instead:

GET /cafe/v1/forms/references?token={signed settings}&field={field key}&search=…&page=1

It answers only for fields of that form (including sub-fields inside its Collections), and only to people who may use the form. Results follow the field's own settings (post types, statuses, taxonomies, roles). The post being edited is never offered to itself.

#What is checked on submit

Every picked ID must still be allowed by the field's settings (right post type, published or allowed status, existing term, user with an allowed role). Anything else is refused with the field's message.

#Taxonomy fields vs post_terms

• A Taxonomy field stores terms as a CAFE value (and can also set the post's terms, if the field is set to). Searchable, good for large taxonomies.
• post_terms in the form shows simple checkboxes and sets the post's terms directly. Good for a few categories.