Allow skipping ValidationWrapper for introspection queries

[kyri-petrou]

Introspection queries are relatively large + deep, so in order for introspection to be allowed we need for these wrappers to allow 250+ fields and 12 levels depth. With this PR, we can disable these checks for introspection queries.

One other way that this could be implemented is to be able to set a separate limit for introspections, e.g.,:

def maxFields(maxFields: Int, maxIntrospectionFields: Option[Int] = None): ValidationWrapper[Any] = ???

Thoughts?

EDIT: This PR now adds the skipForIntrospection method which returns a new ValidationWrapper that is skipped for introspection queries.

[frekw]

In my opinion we should always skip it for introspection. Not much point of having it in that case, right?

[kyri-petrou]

In my opinion we should always skip it for introspection. Not much point of having it in that case, right?

Ideally I think we should do this, I agree. My main concern though is that our isIntrospection check is not particularly strict, so we probably want to be able to give the option to limit introspection queries as well.

This is the main reason I'm also partially inclined for the method to accept a maxIntrospectionFields: Option[Int] argument instead.

[ghostdogpr]

How about something more generic, like def skipForIntrospection(validationWrapper: ValidationWrapper): ValidationWrapper, that would check if it's introspection and run or not the inner wrapper. It feels more re-usable and prevent adding a boolean everywhere.
Maybe we can add some syntax to make it nicer.

[kyri-petrou]

@ghostdogpr what do you think about making it a final method on ValidationWrapper? Or do you prefer having it as a method / syntax in Wrappers which we can import instead?

[ghostdogpr]

Method sounds good!

[kyri-petrou]

@ghostdogpr I'll add a unit test just in case before merging in

[kyri-petrou]

@ghostdogpr turns out we can't simply override apply and |+|. Do we think there might be cases where someone implemented custom logic in those methods?

For apply, I could get this to work, but looks rather weird so I left it out - let me know if you think we should add it:

override def apply[R1 <: R](that: GraphQL[R1]): GraphQL[R1] = super.apply(self.apply(that))

[ghostdogpr]

It's probably okay