implement users resource and email based auth

src/main/java/wtf/beatrice/releasehive/config/ApplicationConfiguration.java

@@ -24,7 +24,7 @@ public class ApplicationConfiguration
 
     @Bean
     UserDetailsService userDetailsService() {
-        return username -> userRepository.findByEmail(username)
+        return email -> userRepository.findByEmail(email)
                 .orElseThrow(() -> new UsernameNotFoundException("User not found"));
     }