[1.0.0-alpha2] Add content display overrides

Problem/Motivation

Now we have a:

• a (WIP) entity view display integration in display_builder_entity_view
• an experimental ui_patterns_field sub-module in UI Patterns 2

We can start working on content display overrides

Proposed resolution

Implement it like layout builder. With a "Display" tabs, instead of a "Layout" tab, in the entity edit tabs.

Locked / unlocked sub trees

Can we implement a layout_builder_lock → like mechanism?

Layout Builder Lock allows administrators to lock sections of a default layout so users can't perform certain actions when overriding the layout for an individual entity.

Because we work on tree structure instead of flat sections, it is best described → like that:

the ability to lock/unlock slots and component subtrees allows the Site Builder to define the creative freedom of the Content Creator on a per-content type basis, which is another way of saying: controlling how rigid/consistent/enforced the layouts are.

It may be a new "special" State property of the display builder, alongside _instance_id & _third_party_settings.

Translation

What do we decide?

• Symmetric translations: The translations have the same state data tree, but some values (mostly strings…) need to be translated.
• Asymmetric translations: The translations can have different data trees. The simpler solution.

Anyway, translations mechanisms must be implemented and managed at StateManager level and be the same for content display overrides and other translations uses cases (config translation of displays, of views...)

An override by display?

Layout Builder is allowing only the override of default display. I beleive Experience builder has not reached the moment they need to thing about that yet.

What do we do?

Restrictions

No need for a mechanism like layout_builder_restrictions → or layout_builder_restrictions_by_role → because it will be managed by the intersection between:

• ✨ [1.0.0-alpha1] Make Island plugins configurable Active
• Display Builder config entity availability according to roles or permissions