src/Tomahawk/Authentication/User/InMemoryUserProvider.php
public function findUserByUsername($username)
    {
        return isset($this->users[strtolower($username)]) ?
            $this->users[strtolower($username)] : null;
    }
public function findUserByUsername($username)
    {
        return isset($this->users[strtolower($username)]) ?
            $this->users[strtolower($username)] : null;
    }
Find user by username

@param $username
@return UserInterface|null