How to fix single_identity_not_deletable: Cannot delete the only identity in Supabase

const { data: { user } } = await supabase.auth.getUser();

if (user && user.identities) {
  console.log(`User has ${user.identities.length} identities`);
  console.log(user.identities);
}

// First, link the new identity (e.g., Google OAuth)
const { data, error: linkError } = await supabase.auth.linkIdentity({
  provider: 'google'
});

if (linkError) {
  console.error('Error linking identity:', linkError);
  return;
}

// Wait for the linking process to complete
// The user will be redirected to the OAuth provider

// After successful linking, you can now unlink the old identity
const { data: unlinkData, error: unlinkError } = await supabase.auth.unlinkIdentity({
  identity_id: 'old-identity-id'
});

async function handleUnlinkIdentity(identityId: string) {
  const { data: { user } } = await supabase.auth.getUser();
  
  // Check if user has multiple identities
  if (user?.identities && user.identities.length <= 1) {
    alert('Cannot remove your only login method. Please add another identity first.');
    return;
  }
  
  const { error } = await supabase.auth.unlinkIdentity({
    identity_id: identityId
  });
  
  if (error) {
    if (error.message.includes('single_identity_not_deletable')) {
      alert('You must have at least one identity linked to your account.');
    } else {
      console.error('Error unlinking identity:', error);
    }
  }
}