Refactor MIME type check in storage service

Replace loop-based MIME type check with Set.prototype.has for improved readability and performance. This change eliminates the need for an explicit loop, making the code more concise and efficient.

apps/backend/src/app/storage/storage.service.ts

@@ -58,8 +58,7 @@ export class StorageService {
 		 * @return {boolean} - True if the current MIME type is allowed, false otherwise.
 		 */
 		function checkMime(allowedMime: Set<string>, currentMime: string): boolean {
-			for (const mime of allowedMime) if (mime === currentMime) return true;
-			return false;
+			return allowedMime.has(currentMime);
 		}
 
 		const fileType = await FileType.fileTypeFromBuffer(file);