Add tests for ID scalar coercion with Guid and int64 values

[Copilot]

Using IDType (GraphQL built-in ScalarDefinition<string>) with a System.Guid .NET field previously threw "Object must implement IConvertible" because the old coerceIDValue<t> used Convert.ChangeType, which requires IConvertible.

The fix was already present in coerceIdValue via the | _ -> Some(string x) fallback (calling ToString() on any value). This PR adds test coverage to lock in that behaviour.

Changes

• ExecutionTests.fs: Two end-to-end execution tests exercising coerceIdValue with non-string values through the AutoField path:
  • Guid-backed ID field — the exact scenario from the original issue
  • int64-backed ID field — exercises the same | _ -> Some(string x) fallback branch with a different non-IConvertible type

type PersonWithGuidId  = { Id: Guid;  Name: string }
type PersonWithInt64Id = { Id: int64; Name: string }

// Both use AutoField so coerceIdValue receives the boxed native value (Guid / int64),
// hitting the | _ -> Some(string x) branch rather than the :? string fast path.
let PersonType =
    Define.Object<PersonWithGuidId>(
        "Person",
        [ Define.AutoField("id", IDType)   // was crashing before fix
          Define.AutoField("name", StringType) ])

Note: explicit Define.Field(..., IDType, resolver) resolvers are constrained by F# type inference to return string (because IDType : ScalarDefinition<string>), so Guid/int64 coercion can only be exercised end-to-end through AutoField.

• CoercionTests.fs: Direct CoerceOutput unit tests verifying IDType serializes string, int, int64, and Guid values to their expected string representations.

[Copilot]

Pull request overview

This PR adds regression coverage for ID scalar output coercion when .NET values include Guid, especially around GraphQL IDType serialization.

Changes:

• Adds direct IDType.CoerceOutput tests for string, int, int64, and Guid values.
• Adds execution tests for a Person object with a Guid-backed ID field through AutoField and explicit Field definitions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/FSharp.Data.GraphQL.Tests/Variables and Inputs/CoercionTests.fs	Adds scalar output coercion coverage for IDType.
tests/FSharp.Data.GraphQL.Tests/ExecutionTests.fs	Adds end-to-end execution tests for Guid-backed ID fields.

[xperiandri]

@copilot is it true?

[Copilot]

Yes, the reviewer was correct. Because IDType : ScalarDefinition<string>, the F# type system constrains any explicit Define.Field(..., IDType, ...) resolver to return string — so coerceIdValue only ever saw a boxed string, never a Guid.

Fixed in 3a79315: replaced that test with Execution handles ID scalar: serializes int64 field via AutoField, which uses AutoField on a PersonWithInt64Id.Id : int64 field. The auto-generated resolver returns a boxed int64, exercising the | _ -> Some(string x) fallback branch in coerceIdValue with a different non-IConvertible-reliant type.

[xperiandri]

@copilot apply changes based on this feedback