This commit adds a new boolean field, "mock", to the `ReportRequestBody` class. This additional field is in line with the new requirements to specify whether the report is a mock or not.
The `toJson()` method is also updated to include this new field during serialization.
This commit introduces a new Dart class, `ReportRequestBody`, which represents the request body for generating reports in the `BenchmarkService`. The class includes a `toJson` method for easy serialization to JSON format.
- `category`: Specifies the category of the report (e.g., "coding").
- `tests`: A list of tests to be included in the report.
