added commissioning endpoint

src/validators/file.validator.ts

@@ -0,0 +1,19 @@
+import {
+  ValidatorConstraint,
+  ValidatorConstraintInterface,
+  ValidationArguments,
+} from 'class-validator';
+
+@ValidatorConstraint({ name: 'fileValidator', async: false })
+export class FileValidator implements ValidatorConstraintInterface {
+  constructor(private readonly allowedMimeTypes: string[]) {}
+
+  validate(file: Express.Multer.File, _args: ValidationArguments) {
+    if (!file || !file.mimetype) return false;
+    return this.allowedMimeTypes.includes(file.mimetype);
+  }
+
+  defaultMessage(_args: ValidationArguments) {
+    return 'Invalid file type';
+  }
+}