Display membership (group relationship) base fields

Problem/Motivation

I see from the group_relationship_field_data database table that some additional info like created and changed timestamps are stored, so why can't we display them on the relationship page?

Proposed resolution

Allow managing these base fields on the Manage display tab of the group_membership content:

• type
• langcode
• already supported
• gid (Group id -> renderable Entity)
• already supported
• created (Timestamp -> Date)
• changed (Timestamp -> Date)
• plugin_id
• group_type

Remaining tasks

Similar features could be added to the Node relationships..

User interface changes

API changes

Data model changes