fix(nip09): honour a tags in deletion requests

A kind-5 request could only name events by `e` tag. Worse, one that
carried `a` tags and no `e` tags built a filter with an empty id list,
which matched every event by that author and marked them all deleted.

Handle `a` tags per NIP-09: parse `kind:pubkey:d` (the `d` value may
contain ':'), require the pubkey to be the request author and the kind
to be replaceable or addressable, and remove only versions up to the
request's `created_at` so a later re-publication survives. An empty
`d` addresses a replaceable kind.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013Tbyw6FwjhEJg3gHfPHxWt
(cherry picked from commit e695f9c66881d3d520d40f0cd3e9c95d9435938c)

tests/test_nip09.py

@@ -0,0 +1,137 @@
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from ..crud import create_event, get_events
+from ..relay.client_connection import NostrClientConnection
+from ..relay.event import NostrEvent
+from ..relay.filter import NostrFilter
+from ..relay.relay import RelaySpec
+
+ALICE = "a" * 64
+BOB = "b" * 64
+SIG = "0" * 128
+
+
+def _connection(relay_id: str) -> NostrClientConnection:
+    conn = NostrClientConnection(relay_id=relay_id, websocket=MagicMock())
+    conn.get_client_config = lambda: RelaySpec()
+    conn._send_msg = AsyncMock()  # type: ignore[method-assign]
+    return conn
+
+
+def _event(relay_id, id_, pubkey, kind, created_at, tags=None) -> NostrEvent:
+    return NostrEvent(
+        id=id_.rjust(64, "0"),
+        relay_id=relay_id,
+        publisher=pubkey,
+        pubkey=pubkey,
+        created_at=created_at,
+        kind=kind,
+        tags=tags or [],
+        content="",
+        sig=SIG,
+    )
+
+
+async def _remaining(relay_id: str) -> set[str]:
+    events = await get_events(relay_id, NostrFilter(kinds=[1, 3, 30023]), False)
+    return {e.id.lstrip("0") or "0" for e in events}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_deletes_only_the_addressed_event():
+    relay_id = "nip09_a_tag"
+    await create_event(_event(relay_id, "1", ALICE, 30023, 100, [["d", "one"]]))
+    await create_event(_event(relay_id, "2", ALICE, 30023, 100, [["d", "two"]]))
+    await create_event(_event(relay_id, "3", BOB, 30023, 100, [["d", "one"]]))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"30023:{ALICE}:one"]])
+    )
+
+    assert await _remaining(relay_id) == {"2", "3"}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_keeps_versions_newer_than_the_request():
+    relay_id = "nip09_until"
+    await create_event(_event(relay_id, "1", ALICE, 30023, 100, [["d", "one"]]))
+    await create_event(_event(relay_id, "2", ALICE, 30023, 300, [["d", "one"]]))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"30023:{ALICE}:one"]])
+    )
+
+    assert await _remaining(relay_id) == {"2"}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_for_replaceable_kind_has_empty_d():
+    relay_id = "nip09_replaceable"
+    await create_event(_event(relay_id, "1", ALICE, 3, 100))
+    await create_event(_event(relay_id, "2", ALICE, 1, 100))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"3:{ALICE}:"]])
+    )
+
+    assert await _remaining(relay_id) == {"2"}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_for_non_addressable_kind_is_ignored():
+    relay_id = "nip09_kind1"
+    await create_event(_event(relay_id, "1", ALICE, 1, 100))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"1:{ALICE}:"]])
+    )
+
+    assert await _remaining(relay_id) == {"1"}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_d_value_may_contain_colons():
+    relay_id = "nip09_colon"
+    await create_event(_event(relay_id, "1", ALICE, 30023, 100, [["d", "a:b:c"]]))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"30023:{ALICE}:a:b:c"]])
+    )
+
+    assert await _remaining(relay_id) == set()
+
+
+@pytest.mark.asyncio
+async def test_e_tag_deletes_only_own_events():
+    relay_id = "nip09_e_tag"
+    await create_event(_event(relay_id, "1", ALICE, 1, 100))
+    await create_event(_event(relay_id, "2", BOB, 1, 100))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(
+            relay_id,
+            "9",
+            ALICE,
+            5,
+            200,
+            [["e", "1".rjust(64, "0")], ["e", "2".rjust(64, "0")]],
+        )
+    )
+
+    assert await _remaining(relay_id) == {"2"}
+
+
+@pytest.mark.asyncio
+async def test_a_tag_with_empty_d_on_addressable_kind_is_specific():
+    relay_id = "nip09_empty_d"
+    await create_event(_event(relay_id, "1", ALICE, 30023, 100))
+    await create_event(_event(relay_id, "2", ALICE, 30023, 100, [["d", ""]]))
+    await create_event(_event(relay_id, "3", ALICE, 30023, 100, [["d", "one"]]))
+
+    await _connection(relay_id)._handle_delete_event(
+        _event(relay_id, "9", ALICE, 5, 200, [["a", f"30023:{ALICE}:"]])
+    )
+
+    assert await _remaining(relay_id) == {"3"}