add createUser mutation

app/graphql/mutations/create_user.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+module Mutations
+  class CreateUser < BaseMutation
+    field :success, Boolean, null: false
+
+    argument :user, Inputs::UserAttributesInput, required: true
+
+    def resolve(user:)
+      User.create!({ **user, email: context[:current_auth].email })
+
+      { success: true }
+    rescue ActiveRecord::RecordInvalid => e
+      { success: false, errors: [e.message] }
+    end
+  end
+end