Add JWT authorization

src/main/java/com/faf223/expensetrackerfaf/repository/UserRepository.java

@@ -3,5 +3,8 @@ package com.faf223.expensetrackerfaf.repository;
 import com.faf223.expensetrackerfaf.model.User;
 import org.springframework.data.jpa.repository.JpaRepository;
 
+import java.util.Optional;
+
 public interface UserRepository extends JpaRepository<User, Long> {
+    Optional<User> findByEmail(String username);
 }