added chats with another users

src/main/java/com/krylov/refound/service/UserService.java

@@ -77,4 +77,9 @@ public class UserService {
         .avatar(user.getAvatarUrl())
         .build();
   }
+
+  public Long getUserIdByLogin(String login) {
+    return repository.findUserByLogin(login)
+        .orElseThrow(() -> new EntityNotFoundException("User not found"));
+  }
 }