feat: add organization entity, repository, and service

src/main/java/com/slotline/organization/Organization.java

@@ -0,0 +1,53 @@
+package com.slotline.organization;
+
+import jakarta.persistence.Column;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+
+import java.time.Instant;
+
+@Entity
+@Table(name = "organization")
+public class Organization {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    private Long id;
+
+    @Column(nullable = false, length = 128)
+    private String name;
+
+    @Column(nullable = false, unique = true, length = 64)
+    private String slug;
+
+    @Column(name = "created_at", nullable = false)
+    private Instant createdAt;
+
+    protected Organization() {
+    }
+
+    public Organization(String name, String slug, Instant createdAt) {
+        this.name = name;
+        this.slug = slug;
+        this.createdAt = createdAt;
+    }
+
+    public Long getId() {
+        return id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getSlug() {
+        return slug;
+    }
+
+    public Instant getCreatedAt() {
+        return createdAt;
+    }
+}

src/main/java/com/slotline/organization/OrganizationRepository.java

@@ -0,0 +1,15 @@
+package com.slotline.organization;
+
+import org.springframework.data.jpa.repository.JpaRepository;
+
+import java.util.List;
+import java.util.Optional;
+
+public interface OrganizationRepository extends JpaRepository<Organization, Long> {
+
+    Optional<Organization> findBySlug(String slug);
+
+    boolean existsBySlug(String slug);
+
+    List<Organization> findAllByOrderByCreatedAtAsc();
+}

src/main/java/com/slotline/organization/OrganizationService.java

@@ -0,0 +1,51 @@
+package com.slotline.organization;
+
+import com.slotline.common.NotFoundException;
+import com.slotline.common.SlugTakenException;
+import com.slotline.organization.dto.OrganizationRequest;
+import com.slotline.organization.dto.OrganizationResponse;
+import org.springframework.stereotype.Service;
+import org.springframework.transaction.annotation.Transactional;
+
+import java.time.Instant;
+import java.util.List;
+
+@Service
+public class OrganizationService {
+
+    public static final String defaultSlug = "default";
+
+    private final OrganizationRepository organizations;
+
+    public OrganizationService(OrganizationRepository organizations) {
+        this.organizations = organizations;
+    }
+
+    @Transactional
+    public OrganizationResponse create(OrganizationRequest request) {
+        if (organizations.existsBySlug(request.slug())) {
+            throw new SlugTakenException(request.slug());
+        }
+        Organization organization = new Organization(request.name(), request.slug(), Instant.now());
+        return OrganizationResponse.from(organizations.save(organization));
+    }
+
+    @Transactional(readOnly = true)
+    public List<OrganizationResponse> findAll() {
+        return organizations.findAllByOrderByCreatedAtAsc().stream()
+                .map(OrganizationResponse::from)
+                .toList();
+    }
+
+    @Transactional(readOnly = true)
+    public Organization require(Long id) {
+        return organizations.findById(id)
+                .orElseThrow(() -> new NotFoundException("Organization " + id + " not found"));
+    }
+
+    @Transactional(readOnly = true)
+    public Organization requireBySlug(String slug) {
+        return organizations.findBySlug(slug)
+                .orElseThrow(() -> new NotFoundException("Organization '" + slug + "' not found"));
+    }
+}