feat(page): add canPageBeUnfurled predicate for Slack link previews

apps/server/src/database/repos/page/page.repo.ts

@@ -423,6 +423,34 @@ export class PageRepo {
     });
   }
 
+  async canPageBeUnfurled(pageId: string, workspaceId: string): Promise<boolean> {
+    const result = await this.db
+      .selectFrom('pages')
+      .innerJoin('spaces', 'spaces.id', 'pages.spaceId')
+      .innerJoin('groups', (join) =>
+        join
+          .onRef('groups.workspaceId', '=', 'spaces.workspaceId')
+          .on('groups.isDefault', '=', true)
+          .on('groups.deletedAt', 'is', null),
+      )
+      .innerJoin('spaceMembers', (join) =>
+        join
+          .onRef('spaceMembers.spaceId', '=', 'spaces.id')
+          .onRef('spaceMembers.groupId', '=', 'groups.id'),
+      )
+      .leftJoin('pageAccess', 'pageAccess.pageId', 'pages.id')
+      .leftJoin('pagePermissions', 'pagePermissions.pageAccessId', 'pageAccess.id')
+      .select(['pages.id'])
+      .where('pages.id', '=', pageId)
+      .where('pages.workspaceId', '=', workspaceId)
+      .where('pages.deletedAt', 'is', null)
+      .where('pagePermissions.id', 'is', null)
+      .limit(1)
+      .executeTakeFirst();
+
+    return !!result;
+  }
+
   withSpace(eb: ExpressionBuilder<DB, 'pages'>) {
     return jsonObjectFrom(
       eb