feat: add nextcloud notification provider (#5343)

* feat: add Nextcloud notification provider
fix: resolve hydration error in add-board modal

* Update packages/integrations/src/nextcloud/nextcloud.integration.ts

Co-authored-by: Manuel <30572287+manuel-rw@users.noreply.github.com>

* Update nextcloud.integration.ts

* defined notificationSchema outside of class

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Co-authored-by: Lorinc936 <lorinc1231@gmail.com>
Co-authored-by: Lorinc936 <116025544+Lorinc936@users.noreply.github.com>

packages/widgets/src/iframe/component.tsx

@@ -119,4 +119,5 @@ const permissionMapping = {
   allowGeolocation: "geolocation",
   allowMicrophone: "microphone",
   allowPayment: "payment",
+  allowModals: "allow-modals",
 } satisfies Record<keyof Omit<WidgetComponentProps<"iframe">["options"], "embedUrl" | "allowScrolling">, string>;