feat: add like/unlike toggle on blog posts with per-user tracking

- PostLike domain entity (post_id, liked_by) with BaseEntity integration
- Post entity: add like_count field (default 0) and to_dict serialization
- PostRepository interface: add get_like, add_like, remove_like methods
- TogglePostLikeUseCase: toggle logic (like → unlike, unlike → like)
- PostResponseDTO/PostResponseSchema: add like_count field
- PostLikeORM model with FK to posts and cascade delete
- SQLAlchemyPostRepository: implement like query/add/remove with ORM mapping
- DI provider registration for TogglePostLikeUseCase
- API endpoint POST /api/v1/posts/{id}/like (auth required)
- Unit tests: PostLike entity, Post.like_count, TogglePostLikeUseCase (7 tests)
- API tests: POST /api/v1/posts/{id}/like (4 tests)
- Test model files: FEATURE_LIKES.md, TEST_MODEL.md updated

app/infrastructure/database/models.py

@@ -7,8 +7,8 @@ Models are used by repositories for data persistence.
 from datetime import UTC, datetime
 from uuid import uuid4
 
-from sqlalchemy import JSON, Boolean, DateTime, String, Text
-from sqlalchemy.orm import Mapped, declarative_base, mapped_column
+from sqlalchemy import JSON, Boolean, DateTime, ForeignKey, String, Text
+from sqlalchemy.orm import Mapped, declarative_base, mapped_column, relationship
 
 Base = declarative_base()
 
@@ -42,6 +42,10 @@ class PostORM(Base):  # type: ignore[valid-type,misc]
     slug: Mapped[str] = mapped_column(String(200), nullable=False, unique=True, index=True)
     author_id: Mapped[str] = mapped_column(String(100), nullable=False, index=True)
     published: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False, index=True)
+    like_count: Mapped[int] = mapped_column(default=0, nullable=False)
+    likes: Mapped[list["PostLikeORM"]] = relationship(
+        back_populates="post", cascade="all, delete-orphan"
+    )
     tags: Mapped[list[str]] = mapped_column(JSON, default=list)
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),
@@ -54,3 +58,32 @@ class PostORM(Base):  # type: ignore[valid-type,misc]
         onupdate=lambda: datetime.now(UTC),
         nullable=False,
     )
+
+
+class PostLikeORM(Base):  # type: ignore[valid-type,misc]
+    """SQLAlchemy model for PostLike.
+
+    Database table representation of post likes.
+    Maps to the 'post_likes' table tracking which users/devices liked which posts.
+
+    Attributes:
+        id: Primary key as UUID string.
+        post_id: Foreign key to the liked post.
+        liked_by: User ID or device identifier.
+        created_at: Creation timestamp.
+    """
+
+    __tablename__ = "post_likes"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid4()))
+    post_id: Mapped[str] = mapped_column(
+        String(36), ForeignKey("posts.id", ondelete="CASCADE"), nullable=False, index=True
+    )
+    liked_by: Mapped[str] = mapped_column(String(200), nullable=False, index=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True),
+        default=lambda: datetime.now(UTC),
+        nullable=False,
+    )
+
+    post: Mapped[PostORM] = relationship(back_populates="likes")

app/infrastructure/di/providers.py

@@ -15,6 +15,7 @@ from app.application import (
     GetPostUseCase,
     ListPostsUseCase,
     PublishPostUseCase,
+    TogglePostLikeUseCase,
     UpdatePostUseCase,
 )
 from app.application.interfaces import TransactionManager
@@ -236,6 +237,26 @@ class UseCaseProvider(Provider):
             tx_manager=tx_manager,
         )
 
+    @provide(scope=Scope.REQUEST)
+    def get_toggle_like_use_case(
+        self,
+        post_repo: PostRepository,
+        tx_manager: TransactionManager,
+    ) -> TogglePostLikeUseCase:
+        """Provide TogglePostLikeUseCase.
+
+        Args:
+            post_repo: Post repository dependency.
+            tx_manager: Transaction manager dependency.
+
+        Returns:
+            Configured TogglePostLikeUseCase instance.
+        """
+        return TogglePostLikeUseCase(
+            post_repo=post_repo,
+            tx_manager=tx_manager,
+        )
+
 
 class KeycloakProvider(Provider):
     """Provider for Keycloak authentication client.

app/infrastructure/repositories/post.py

@@ -10,9 +10,10 @@ from sqlalchemy import or_, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.domain.entities import Post
+from app.domain.entities.like import PostLike
 from app.domain.repositories import PostRepository
 from app.domain.value_objects import Content, Slug, Title
-from app.infrastructure.database.models import PostORM
+from app.infrastructure.database.models import PostLikeORM, PostORM
 
 
 class SQLAlchemyPostRepository(PostRepository):
@@ -53,6 +54,7 @@ class SQLAlchemyPostRepository(PostRepository):
             slug=Slug(orm.slug),
             author_id=orm.author_id,
             published=orm.published,
+            like_count=orm.like_count,
             tags=orm.tags or [],
             created_at=orm.created_at,
             updated_at=orm.updated_at,
@@ -74,6 +76,7 @@ class SQLAlchemyPostRepository(PostRepository):
             slug=post.slug.value,
             author_id=post.author_id,
             published=post.published,
+            like_count=post.like_count,
             tags=post.tags,
             created_at=post.created_at,
             updated_at=post.updated_at,
@@ -124,6 +127,7 @@ class SQLAlchemyPostRepository(PostRepository):
         orm.content = entity.content.value
         orm.slug = entity.slug.value
         orm.published = entity.published
+        orm.like_count = entity.like_count
         orm.tags = entity.tags
         orm.updated_at = entity.updated_at
 
@@ -284,3 +288,60 @@ class SQLAlchemyPostRepository(PostRepository):
         result = await self._session.execute(stmt)
         orms = result.scalars().all()
         return [self._to_domain(orm) for orm in orms]
+
+    async def get_like(self, post_id: UUID, liked_by: str) -> PostLike | None:
+        """Get a like by post and user/device.
+
+        Args:
+            post_id: UUID of the post.
+            liked_by: User ID or device ID.
+
+        Returns:
+            PostLike if found, None otherwise.
+        """
+        result = await self._session.execute(
+            select(PostLikeORM).where(
+                PostLikeORM.post_id == str(post_id),
+                PostLikeORM.liked_by == liked_by,
+            )
+        )
+        orm = result.scalar_one_or_none()
+        if not orm:
+            return None
+        return PostLike(
+            id=UUID(orm.id),
+            post_id=UUID(orm.post_id),
+            liked_by=orm.liked_by,
+            created_at=orm.created_at,
+        )
+
+    async def add_like(self, like: PostLike) -> None:
+        """Add a new like.
+
+        Args:
+            like: PostLike entity to add.
+        """
+        orm = PostLikeORM(
+            id=str(like.id),
+            post_id=str(like.post_id),
+            liked_by=like.liked_by,
+            created_at=like.created_at,
+        )
+        self._session.add(orm)
+
+    async def remove_like(self, post_id: UUID, liked_by: str) -> None:
+        """Remove a like by post and user/device.
+
+        Args:
+            post_id: UUID of the post.
+            liked_by: User ID or device ID.
+        """
+        result = await self._session.execute(
+            select(PostLikeORM).where(
+                PostLikeORM.post_id == str(post_id),
+                PostLikeORM.liked_by == liked_by,
+            )
+        )
+        orm = result.scalar_one_or_none()
+        if orm:
+            await self._session.delete(orm)