Persist privacy-safe submission rate limits

apps/api/alembic/versions/0007_persistent_rate_limit.py

@@ -0,0 +1,25 @@
+"""Persistent privacy-preserving submission rate limit."""
+from alembic import op
+import sqlalchemy as sa
+
+revision = "0007"
+down_revision = "0006"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "submission_attempt",
+        sa.Column("id", sa.Uuid(), primary_key=True),
+        sa.Column("client_hash", sa.String(64), nullable=False),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False),
+    )
+    op.create_index("ix_submission_attempt_client_hash", "submission_attempt", ["client_hash"])
+    op.create_index("ix_submission_attempt_created_at", "submission_attempt", ["created_at"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_submission_attempt_created_at", table_name="submission_attempt")
+    op.drop_index("ix_submission_attempt_client_hash", table_name="submission_attempt")
+    op.drop_table("submission_attempt")