REST: Filter out non-top-level schemas from OAS

This adds a redocly decorator that removes any schemas not listed in
`specs/global/schemas.json`.

Bug: T377321
Change-Id: Ib662871d0d3ea1a2088c08ee8e6d1d5dda68aee4

repo/rest-api/redocly.yaml

@@ -3,3 +3,9 @@ extends:
 
 rules:
   security-defined: off
+
+plugins:
+  - ./redocly/plugin-filter-schemas.js
+
+decorators:
+  filterSchemas/filterSchemas: on

repo/rest-api/redocly/.eslintrc.json

@@ -0,0 +1,7 @@
+{
+	"extends": "wikimedia/server",
+	"rules": {
+		"max-len": [ "error", 120 ],
+		"no-console": "error"
+	}
+}

repo/rest-api/redocly/plugin-filter-schemas.js

@@ -0,0 +1,31 @@
+'use strict';
+
+module.exports = function () {
+	return {
+		id: 'filterSchemas',
+		decorators: {
+			oas3: {
+				filterSchemas: function () {
+					let originalSchemas;
+
+					return {
+						Components: {
+							leave( components ) {
+								for ( const key in components.schemas || {} ) {
+									if ( originalSchemas[ key ] === undefined ) {
+										delete components.schemas[ key ];
+									}
+								}
+							},
+							NamedSchemas: {
+								enter( schemas ) {
+									originalSchemas = schemas;
+								}
+							}
+						}
+					};
+				}
+			}
+		}
+	};
+};