feat(statehub): add offline write buffer relay

migrations/versions/e9f0a1b2c3d4_write_idempotency_keys.py

@@ -0,0 +1,43 @@
+"""add write idempotency keys
+
+Revision ID: e9f0a1b2c3d4
+Revises: d8e9f0a1b2c3
+Create Date: 2026-06-23
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import JSONB, UUID
+
+revision = "e9f0a1b2c3d4"
+down_revision = "d8e9f0a1b2c3"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "write_idempotency_keys",
+        sa.Column("id", UUID(as_uuid=True), primary_key=True),
+        sa.Column("key", sa.String(length=200), nullable=False),
+        sa.Column("method", sa.String(length=10), nullable=False),
+        sa.Column("path", sa.Text(), nullable=False),
+        sa.Column("route_class", sa.String(length=30), nullable=False),
+        sa.Column("request_hash", sa.String(length=64), nullable=False),
+        sa.Column("response_status", sa.Integer(), nullable=False),
+        sa.Column("response_body", JSONB(), nullable=True),
+        sa.Column("source_host", sa.String(length=200), nullable=True),
+        sa.Column("source_agent", sa.String(length=100), nullable=True),
+        sa.Column("first_seen_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("last_seen_at", sa.DateTime(timezone=True), nullable=False),
+        sa.Column("expires_at", sa.DateTime(timezone=True), nullable=True),
+        sa.UniqueConstraint("key", name="uq_write_idempotency_keys_key"),
+    )
+    op.create_index("ix_write_idempotency_keys_key", "write_idempotency_keys", ["key"])
+    op.create_index("ix_write_idempotency_keys_expires_at", "write_idempotency_keys", ["expires_at"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_write_idempotency_keys_expires_at", table_name="write_idempotency_keys")
+    op.drop_index("ix_write_idempotency_keys_key", table_name="write_idempotency_keys")
+    op.drop_table("write_idempotency_keys")