Federation Subgraph: add validation for used fields

[meskill]

Resolvers on types could use different fields from the respective type inside the resolver itself.

Add a validation that every field that is used as .value.field_name inside the resolver is actually part of the type and if not generated a Validation error with info about unknown field. Make sure nested paths .value.a.b.c are covered as well.

Good Example

type User @http(path: "/users/{{.value.id}}") {
  id: ID
  name: String
}

Bad Examples

type User @http(path: "/users/{{.value.foo.id}}") {
  id: ID
  name: String
}

type User @http(path: "/users/{{.value.age}}") {
  id: ID
  name: String
}

[tusharmath]

/bounty $50

[algora-pbc]

💎 $50 bounty • Tailcall Inc.

Steps to solve:

1. Start working: Comment /attempt #2911 with your implementation plan
2. Submit work: Create a pull request including /claim #2911 in the PR body to claim the bounty
3. Receive payment: 100% of the bounty is received 2-5 days post-reward. Make sure you are eligible for payouts

🙏 Thank you for contributing to tailcallhq/tailcall!
🧐 Checkout our guidelines before you get started.
💵 More about our bounty program.

Attempt	Started (GMT+0)	Solution
🟢 @dekkku		#2916