Fixed incorrect Content-Type (#174) (#175)

Co-authored-by: Adam Bem <adam.bem@zoho.eu>
Reviewed-on: #175
Reviewed-by: Mikolaj Widla <widlam@noreply.example.com>

Backend/mocked-services/src/main/java/com/r11/tools/controller/MockController.java

@@ -194,6 +194,7 @@ public class MockController {
         MockedMessageDto mockedMessageDto = klausService.getMockedResponse(clientUUID, mockedResponseId);
         HttpHeaders httpHeaders = new HttpHeaders();
         if (mockedMessageDto.getHttpHeaders() != null) mockedMessageDto.getHttpHeaders().forEach(httpHeaders::set);
+        httpHeaders.add("Content-Type", mockedMessageDto.getMediaType());
         return new ResponseEntity<>(mockedMessageDto.getMessageBody(), httpHeaders,
                 Objects.requireNonNull(HttpStatus.valueOf(mockedMessageDto.getHttpStatus())));
     }