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/base.py

@@ -0,0 +1,30 @@
+"""Base model and mixins for all CartSnitch ORM models."""
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, func
+from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
+
+
+class Base(DeclarativeBase):
+    """Base class for all CartSnitch models."""
+
+
+class TimestampMixin:
+    """Mixin providing created_at / updated_at columns."""
+
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+    updated_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), onupdate=func.now(), nullable=False
+    )
+
+
+class UUIDPrimaryKeyMixin:
+    """Mixin providing a UUID primary key."""
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        primary_key=True, default=uuid.uuid4, server_default=func.gen_random_uuid()
+    )