Custom fields with Magic Links/Social Sign Up

I have a custom field referredBy with my user, which stores the referral code they used to sign up. With email/password signup, I use it as follows:

authClient.signUp.email(
  {
    email: data.username,
    password: data.password,
    referredBy: "my-referral-code"
  }
)

authClient.signUp.email(
  {
    email: data.username,
    password: data.password,
    referredBy: "my-referral-code"
  }
)

authClient.signUp.email(
  {
    email: data.username,
    password: data.password,
    referredBy: "my-referral-code"
  }
)

authClient.signUp.email(
  {
    email: data.username,
    password: data.password,
    referredBy: "my-referral-code"
  }
)

I'm unsure on how to populate that field on sign up, when signin up using either magic links or social sign-ups. Does someone have any ideas? Thanks!