Add enum type extension to infer cases via CaseIterable from an enum

Sources/GraphQLKit/Graphiti+Enum.swift

@@ -0,0 +1,13 @@
+import Graphiti
+import Vapor
+
+extension Enum where EnumType: CaseIterable {
+    // Initialize an enum type from a `CaseIterable` enum.
+    public convenience init(
+        _ type: EnumType.Type,
+        name: String? = nil
+    ) {
+        self.init(type, name: name, EnumType.allCases.map({ Value($0) }))
+    }
+}
+