feat(admin, admin-ui, medusa-js, medusa-react, medusa): Support Admin Extensions (#4761)

Co-authored-by: Rares Stefan <948623+StephixOne@users.noreply.github.com>
Co-authored-by: Oli Juhl <59018053+olivermrbl@users.noreply.github.com>

packages/admin-ui/ui/src/providers/widget-provider.tsx

@@ -0,0 +1,38 @@
+import React, { PropsWithChildren, useCallback, useMemo } from "react"
+import WidgetRegistry from "../registries/widget-registry"
+import { InjectionZone, Widget } from "../types/extensions"
+
+type WidgetContextType = {
+  getWidgets: (injectionZone: InjectionZone) => Widget[]
+}
+
+const WidgetContext = React.createContext<WidgetContextType | null>(null)
+
+export const useWidgets = () => {
+  const context = React.useContext(WidgetContext)
+
+  if (!context) {
+    throw new Error("useWidgets must be used within a WidgetContext")
+  }
+
+  return context
+}
+
+type WidgetProviderProps = PropsWithChildren<{
+  registry: WidgetRegistry
+}>
+
+export const WidgetProvider = ({ registry, children }: WidgetProviderProps) => {
+  const getWidgets = useCallback(
+    (injectionZone: InjectionZone) => {
+      return registry.getWidgets(injectionZone)
+    },
+    [registry]
+  )
+
+  const values = useMemo(() => ({ getWidgets }), [getWidgets])
+
+  return (
+    <WidgetContext.Provider value={values}>{children}</WidgetContext.Provider>
+  )
+}