[Suggestion] Data Validations

There should be an option to add custom Scalars to the Tables which will validate the backend while a mutation is called.

For example, I have a `user` table that has `email`.

| user_id | email |
|--------------|-------------|

have a corresponding GQL
```graphql
type Users {
user_id: String!;
email: String!;
}
````

### Suggested Changes
Add support to change these scalars to custom logic.
```graphql
type Users {
user_id: String!;
email: Email!;
}
```
and a custom logic can be written in any of one language, ex. `nodejs`

```javascript
const emailRegexp = /^....email validation regex....$/;

// will return true or error message that needs to be shown
const Email = (input) => emailRegexp.test(input);

```