feat(statehub): add offline write buffer relay

api/models/write_idempotency_key.py

@@ -0,0 +1,32 @@
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+from typing import Any
+
+from sqlalchemy import DateTime, Integer, String, Text, UniqueConstraint
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from api.models.base import Base, new_uuid
+
+
+class WriteIdempotencyKey(Base):
+    __tablename__ = "write_idempotency_keys"
+    __table_args__ = (
+        UniqueConstraint("key", name="uq_write_idempotency_keys_key"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=new_uuid)
+    key: Mapped[str] = mapped_column(String(200), nullable=False, index=True)
+    method: Mapped[str] = mapped_column(String(10), nullable=False)
+    path: Mapped[str] = mapped_column(Text, nullable=False)
+    route_class: Mapped[str] = mapped_column(String(30), nullable=False)
+    request_hash: Mapped[str] = mapped_column(String(64), nullable=False)
+    response_status: Mapped[int] = mapped_column(Integer, nullable=False)
+    response_body: Mapped[Any] = mapped_column(JSONB, nullable=True)
+    source_host: Mapped[str | None] = mapped_column(String(200), nullable=True)
+    source_agent: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    first_seen_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    last_seen_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)
+    expires_at: Mapped[datetime | None] = mapped_column(DateTime(timezone=True), nullable=True, index=True)