Denote which Address/Phone/Email is a Contact's primary

Problem/Motivation

It is helpful to understand which address, phone, and email are a contact's primary, but the existing "addresses", "phones" and "emails" Entity Reference fields on the Contact entity do not denote which referenced entity is the primary for each.

Steps to reproduce

Proposed resolution

Option A

• Adopt convention that the first referenced entity (delta 0) is the primary
• Improve Inline Entity Form UX for these fields to make clear that the first is the primary and adapts when the primary is changed (e.g. via drag and drop)
• Add a "Make primary" button to the Inline Entity Form table for each row (except the first) that brings the given referenced entity to the top of the list

Option B

• Improve as needed Primary Entity Reference → , (which explicitly stores a primary bit with each reference) to ensure that Views, ECA, Search API, Token, etc. be able to navigate the reference as they do vanilla Entity Reference fields
• Replace the existing "addresses", "phones" and "emails" Entity Reference fields with Primary Entity Reference fields

Remaining tasks

User interface changes

API changes

Data model changes