Update notification and membership models, add extension installing method

Several updates are made to the notification model, mainly removing the 'entity_id', 'entity_type', and 'language_code' fields from the properties. We've also updated the 'accounts_memberships' table, by preventing its updates except for 'account_role'.

packages/features/notifications/src/hooks/use-fetch-notifications.ts

@@ -9,8 +9,6 @@ type Notification = {
   type: 'info' | 'warning' | 'error';
   created_at: string;
   link: string | null;
-  entity_id: string | null;
-  entity_type: string | null;
 };
 
 export function useFetchNotifications({
@@ -58,9 +56,7 @@ export function useFetchNotifications({
            dismissed, 
            type, 
            created_at, 
-           link, 
-           entity_id, 
-           entity_type
+           link
            `,
         )
         .in('account_id', accountIds)