Read the channel signing key with its single-key API

tests/test_services.c

@@ -343,7 +343,7 @@ int main(void) {
     uint8_t peer_ed[32], peer_private[64], group_private[32];
     assert(sc_derive_ed25519_pubkey(keys.private_key, peer_ed) == SC_OK);
     SHA512(keys.private_key, 32, peer_private);
-    assert(!topo_node_sqlite_channel_get_privs(db, chat->channel_id, NULL, group_private));
+    assert(!topo_node_sqlite_channel_get_priv(db, chat->channel_id, group_private));
     assert(test_member_seed(inst, chat->channel_id, keys.public_key, peer_ed, peer_private,
         group_private, "{}", NULL, NULL) >= 0);
     struct NODE_CONN_DIRECT* seed = NULL;