FIX: Update ValidationPipe for class-validator 0.14.0+ compatibility

This fix addresses a breaking change introduced in class-validator 0.14.0
where the default for forbidUnknownValues changed from false to true.

Issue:
- POST /connections was returning 400 "an unknown value was passed to the
  validate function" errors
- This occurred because CreateConnectionDto and UpdateConnectionDto have no
  validation decorators, causing class-validator 0.14.0+ to treat them as
  "unknown values"
- Extra fields (like connector_version) in request payloads would fail
  validation

Solution:
- Set forbidUnknownValues: false to allow DTOs without validation decorators
- Set whitelist: true to automatically strip extra properties not defined
  in DTOs
- This maintains backward compatibility while adding security by removing
  unexpected fields

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/pipes/object-validation.pipe.ts

@@ -14,7 +14,10 @@ export class ValidationPipe implements PipeTransform<any> {
       return value;
     }
     const object = plainToInstance(metatype, value);
-    const errors = await validate(object);
+    const errors = await validate(object, {
+      forbidUnknownValues: false,
+      whitelist: true,
+    });
     if (errors.length > 0) {
       const errorMessages = errors.map((err) => err.constraints);
       throw new BadRequestException(errorMessages);