title: Invalid credentials when trying to authenticate with password in Realm
body: <p>I'm trying to authenticate a user with password like this:</p>
  
  <pre><code>let syncCredentials = SyncCredentials.usernamePassword(username: email, password: password, register: true)
  
  SyncUser.logIn(with: syncCredentials, server: Constants.Realm.Server) { (realmUser, error) in
      guard let realmUser = realmUser else {
          DDLogError("\(error)")
  
          return
      }
  
      DDLogInfo("realmUser: \(realmUser)")
  }
  </code></pre>
  
  <p>but it prints out this error:</p>
  
  <blockquote>
    <p>Optional(Error Domain=io.realm.sync Code=611 "The provided credentials are invalid." UserInfo={statusCode=400, NSLocalizedDescription=The provided credentials are invalid.})</p>
  </blockquote>
  
  <p>The <code>Server</code> constant is correct, as I can successfully connect to the Realm Object Server using Facebook credentials.</p>