router-bridge: Introduce native graphql (JS) validate to the plan

[abernix]

While Federation's buildQueryPlan function does a fair bit of validation in order to properly build our plan (and leverages graphql's validate function do most of that), it does not do all of the default validations that are specified.

To be thorough, we must call validate, as we did prior to updating to the new Federation v2 alpha query planner.

This also introduces a number of tests which exercise specific validations which we know as of today are not part of federation:

• invalid_graphql_validation_1_is_caught: NoFragmentCyclesRule
• invalid_graphql_validation_2_is_caught: ScalarLeafsRule
• invalid_graphql_validation_3_is_caught: NoUnusedFragmentsRule

I chose three random but different types to make sure we're capturing it.

Closes: #25

[abernix]

I renamed this just to add clarity — since this is a parsing error, rather than a validation error.

[o0Ignition0o]

Looks good to me!

I feel like some of the validation steps can occur before the actual query pipeline, eg when updating the supergraph schema.

Would it be worth opening an issue on the router, to add schema validation capabilities that would allow us to refuse to update the router with an invalid schema?

[abernix]

@o0Ignition0o That's a prudent observation, and you're correct. We could use validateSDL to do some validations on the schema (which ultimately happen as part of validate, but we could do one better to avoid that schema from going into operation in the Router). (Though practically speaking, I believe our incoming schemas will typically be validated as part of Studio + Composition ahead of time).

I'll open an issue.