Add all layers.

sportshub-infrastructure/src/main/java/org/sportshub/infrastructure/user/adapter/UserInMemoryAdapter.java

@@ -0,0 +1,25 @@
+package org.sportshub.infrastructure.user.adapter;
+
+import java.util.List;
+import java.util.Optional;
+import java.util.UUID;
+
+import org.sportshub.domain.user.model.User;
+import org.sportshub.domain.user.port.UserPort;
+import org.springframework.stereotype.Component;
+
+@Component
+public class UserInMemoryAdapter implements UserPort {
+    private static final List<User> users = List.of(
+        new User(UUID.fromString("c1a0805f-c618-47dc-bae7-bee70503644e"), "password"),
+        new User(UUID.fromString("4eff194d-dd8e-463e-974f-034bfd509f84"), "password"),
+        new User(UUID.fromString("c78d7d7c-0386-415d-86dc-98a470591e07"), "password")
+    );
+
+    @Override
+    public Optional<User> findById(final UUID userId) {
+        return users.stream()
+            .filter(user -> userId.equals(user.id()))
+            .findFirst();
+    }
+}