add experimental directive

graphql2/graph/_directives.graphqls

@@ -7,3 +7,10 @@ directive @goField(
   name: String # overrides the field name in the generated Go code
   omittable: Boolean # creates the field with a wrapper type (graphql.Omittable[T]) with a boolean indicating if the field is null (similar to sql.NullString and friends)
 ) on INPUT_FIELD_DEFINITION | FIELD_DEFINITION
+
+# experimental is used to mark fields as experimental.
+#
+# Experimental fields are subject to change/removal without warning.
+directive @experimental(
+  flagName: String! # the name of the feature flag to use to enable this field
+) on FIELD_DEFINITION

graphql2/graph/destinations.graphqls

@@ -1,6 +1,6 @@
 extend type Query {
-  destinationTypes: [DestinationTypeInfo!]!
-  destinationFieldValidate(input: DestinationFieldValidateInput!): Boolean!
+  destinationTypes: [DestinationTypeInfo!]! @experimental(flagName: "dest-types")
+  destinationFieldValidate(input: DestinationFieldValidateInput!): Boolean! @experimental(flagName: "dest-types")
 }
 
 input DestinationFieldValidateInput {

graphql2/graphqlapp/app.go

@@ -158,7 +158,12 @@ func isGQLValidation(gqlErr *gqlerror.Error) bool {
 
 func (a *App) Handler() http.Handler {
 	h := handler.NewDefaultServer(
-		graphql2.NewExecutableSchema(graphql2.Config{Resolvers: a}),
+		graphql2.NewExecutableSchema(graphql2.Config{
+			Resolvers: a,
+			Directives: graphql2.DirectiveRoot{
+				Experimental: Experimental,
+			},
+		}),
 	)
 
 	type hasTraceKey int

graphql2/graphqlapp/directives.go

@@ -0,0 +1,17 @@
+package graphqlapp
+
+import (
+	"context"
+
+	"github.com/99designs/gqlgen/graphql"
+	"github.com/target/goalert/expflag"
+	"github.com/target/goalert/validation"
+)
+
+func Experimental(ctx context.Context, obj interface{}, next graphql.Resolver, flagName string) (res interface{}, err error) {
+	if !expflag.ContextHas(ctx, expflag.Flag(flagName)) {
+		return nil, validation.NewGenericError("experimental flag not enabled")
+	}
+
+	return next(ctx)
+}