Schema validation for data files

## Is your feature request related to a problem? Please describe
Creating the test data files is laborious and often involves having to reference the relationships etc. to determine the correct (case-sensitive) navigation properties.

## Describe the solution you'd like
It would be great if there was a way to validate the data files (e.g. through a [JSON schema](https://json-schema.org)). Perhaps this could be generated from the users instance? VS Code has built in support for JSON schema validation.