fix: Field resolvers are mutable

This allows us to modify resolvers, which improves our ability to set resolvers after creation, making conversions between AST schemas (that have no resolvers) and executable schemas easier.

Author: NeedleInAJayStack

Sources/GraphQL/Type/Definition.swift

@@ -489,13 +489,17 @@ public struct GraphQLResolveInfo: Sendable {
 
 public typealias GraphQLFieldMap = OrderedDictionary<String, GraphQLField>
 
-public struct GraphQLField: Sendable {
+public struct GraphQLField: @unchecked Sendable {
     public let type: GraphQLOutputType
     public let args: GraphQLArgumentConfigMap
     public let deprecationReason: String?
     public let description: String?
-    public let resolve: GraphQLFieldResolve?
-    public let subscribe: GraphQLFieldResolve?
+
+    /// The resolution logic of the field. This should not be mutated while the schema is being used.
+    public var resolve: GraphQLFieldResolve?
+    /// The subscription logic of the field. This should not be mutated while the schema is being used.
+    public var subscribe: GraphQLFieldResolve?
+
     public let astNode: FieldDefinition?
 
     public init(