Hi, I need some more help. I am getting an error trying to add a custom field to my signup form. Everything works as expected, showing the field with a correct validation, but then when I submit I get an error

400

with the message

"Are you sending too many / too few formFields?"

What am I doing wrong?

import SuperTokensReact from "supertokens-auth-react";
import ThirdPartyEmailPasswordReact from "supertokens-auth-react/recipe/thirdpartyemailpassword";

if (typeof window !== "undefined") {
  SuperTokensReact.init({
    useReactRouterDom: false,
    appInfo: {
      appName: "Confabulists",
        websiteDomain,
        apiDomain: websiteDomain,
        apiBasePath
    },
    recipeList: [
        ThirdPartyEmailPasswordReact.init({
          signInAndUpFeature: {
        defaultToSignUp: true,
        signUpForm: {
          privacyPolicyLink: "https://www.confabulists.com/privacy-policy",
          termsAndConditionsLink: "https://www.confabulists.com/terms-and-conditions",
          formFields: [
        {
          id: "userSlug",
          label: "User Slug",
          placeholder: "",
          validate: async value => {
            return undefined;
          }
        }
          ]
        }
      },
      emailVerificationFeature: {
        mode: "REQUIRED"
      }
        }),
        SessionReact.init()
      ]
  });
}

Thanks!