Meadow is a WordPress Fields API.
WordPress has various content types (e.g. posts, comments, site settings).
A fields API gives you a declarative syntax to register metadata for any type.
UI in the /wp-admin/ interface will be created for users to edit meta.
Third-party applications that interface with a WordPress site (e.g. the WordPress iOS app)
can inspect registered metadata and create UI accordingly.
A meta object (e.g. Meadow_Postmeta)
is an encapsulated piece of metadata. It's defines data-related requirements for metadata,
e.g. sanitization, authorization callbacks, etc. Utilizing existing APIs is preferred
over reinventing the world.
Meta objects are put on a global store so they can be described to third-parties, like the REST API.
A UI control (e.g. Meadow_Postmeta_UI_Control)
configures pieces of UI (think a form field) for a user to edit a meta object inside
the /wp-admin/ interface. A control must be bound to a meta object.
A section is a collection of UI controls (think a metabox or a Settings API section) that fit into a specific place in an admin screen.
Metadata is registered via meadow_register_meta().
Multi-entry support
Should is protected meta affect whether to display meta or not? Probably.