feat: merge cartsnitch/api into api/ subdirectory

Consolidate API gateway service into monorepo.
Squashed from https://github.com/cartsnitch/api main (89bacb1).

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/cartsnitch_api/models/user.py

@@ -0,0 +1,50 @@
+"""User and UserStoreAccount models."""
+
+import uuid
+from datetime import datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import DateTime, ForeignKey, String, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from cartsnitch_api.constants import AccountStatus
+from cartsnitch_api.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
+from cartsnitch_api.types import EncryptedJSON
+
+if TYPE_CHECKING:
+    from cartsnitch_api.models.purchase import Purchase
+    from cartsnitch_api.models.store import Store
+
+
+class User(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Application user."""
+
+    __tablename__ = "users"
+
+    email: Mapped[str] = mapped_column(String(255), nullable=False, unique=True)
+    hashed_password: Mapped[str] = mapped_column(String(255), nullable=False)
+    display_name: Mapped[str | None] = mapped_column(String(100))
+
+    # Relationships
+    store_accounts: Mapped[list["UserStoreAccount"]] = relationship(back_populates="user")
+    purchases: Mapped[list["Purchase"]] = relationship(back_populates="user")
+
+
+class UserStoreAccount(UUIDPrimaryKeyMixin, TimestampMixin, Base):
+    """Link between a user and their retailer account credentials."""
+
+    __tablename__ = "user_store_accounts"
+    __table_args__ = (UniqueConstraint("user_id", "store_id", name="uq_user_store_account"),)
+
+    user_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("users.id"), nullable=False)
+    store_id: Mapped[uuid.UUID] = mapped_column(ForeignKey("stores.id"), nullable=False)
+    session_data: Mapped[dict | None] = mapped_column(EncryptedJSON)
+    session_expires_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    last_sync_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True))
+    status: Mapped[AccountStatus] = mapped_column(
+        String(20), nullable=False, default=AccountStatus.ACTIVE
+    )
+
+    # Relationships
+    user: Mapped["User"] = relationship(back_populates="store_accounts")
+    store: Mapped["Store"] = relationship(back_populates="user_accounts")