@spec absorb(:item | :category, map(), map()) ::
  {:ok, map()} | {:error, {module(), [{atom(), String.t()}]}}

Folds every enabled extension's submitted namespace into data.

For each enabled extension E exporting the kind-appropriate cast callback: takes params[E.key()] (a map, or %{} when absent/nil), calls E.cast_item/2 (or cast_category/2) with the extension's current value data[E.key()] || %{}, and merges the result under data[E.key()]. Stops at the first extension that returns an error.

Same resilience contract as columns/1: a cast that raises, throws, exits, or returns neither {:ok, _} nor {:error, _} is logged and that extension's namespace keeps its current value — one broken extension must not crash the form on every keystroke (absorb/3 runs on validate).

@spec all() :: [module()]

All enabled extension modules contributed by registered PhoenixKit modules, in registration order, deduplicated. An extension whose key/0 is not a string, is empty, is underscore-prefixed, looks like a language code, or names a catalogue-owned data key is dropped (logged once per process) — see @reserved_keys.

@spec columns(:detail_items | :detail_categories) :: [
  PhoenixKitCatalogue.Extension.column()
]

Enabled extensions' contributed columns for the catalogue admin's configurable :detail_items / :detail_categories tables (spec §2 principle 8, §4 row C4's column follow-up — the "Columns" modal on CatalogueDetailLive).

Each contributed id is namespaced under its extension's key/0 ("<key>:<id>") so it can never collide with PhoenixKitCatalogue.Web.TableConfig's own ids or another extension's — enforced by rejecting a key/0 or column id that itself carries the ":" delimiter (see valid_column?/1), so key <> ":" <> id can never mean two different things.

Same resilience contract as sections/1 and absorb/3: a missing, disabled, or raising extension — or one whose item_columns/0/category_columns/0 returns a malformed entry — contributes nothing rather than breaking the page. That contract also covers what happens once a column is actually IN USE: a label or render that raises, throws, exits, or returns a value Phoenix.HTML.Safe can't turn into HTML degrades to a blank label/empty cell for that one column instead of taking down the whole page — see guarded_label/3 and guarded_render/3.

@spec duplicate_data(:item | :category, map()) :: map()

A copied item's or category's data, with each extension's namespace passed through that extension's optional duplicate_data/2: the returned map replaces the namespace, nil drops it. Namespaces with no such callback are copied as they are.

Disabled extensions are asked too — their data is still in the row, and switching a module off must not let a copy carry its external ids. A callback that raises, or returns something else, drops its namespace (logged): a copy without the shop's fields is recoverable, a second row claiming the same external product is not.

@spec owned_keys() :: [String.t()]

The data keys owned by registered extensions, enabled or not — a copy must not mistake one for a language code.

@spec sections(:item | :category) :: [module()]

Enabled extension modules that render a section for kind (:item or :category) — i.e. export item_section/1 (or category_section/1).