Expose feature helper APIs through FFI

We add requires_* counterparts for every supports_* method on
InitFeatures, completing the BOLT 9 feature flag coverage
for FFI consumers.

We export the existing feature helper methods for both InitFeatures
and NodeFeatures through UniFFI. NodeFeatures had the same missing
export path as InitFeatures and was noticed while addressing the
InitFeatures FFI exposure.

Additionally, we extend the Python full-cycle test to cover node
features and init features on their real runtime paths.

Author: enigbe

bindings/python/src/ldk_node/test_ldk_node.py

@@ -121,6 +121,29 @@ def expect_event(node, expected_event_type):
     return event 
 
 
+def assert_feature_helpers_return_bool(test_case, features):
+    feature_methods = [
+        method_name for method_name in dir(features)
+        if method_name.startswith("supports_") or method_name.startswith("requires_")
+    ]
+
+    test_case.assertGreater(len(feature_methods), 0)
+    for method_name in feature_methods:
+        with test_case.subTest(method_name=method_name):
+            test_case.assertIsInstance(getattr(features, method_name)(), bool)
+
+
+def node_features_exposed(test_case, node_features):
+    test_case.assertIsInstance(node_features, NodeFeatures)
+    assert_feature_helpers_return_bool(test_case, node_features)
+
+
+def init_features_exposed(test_case, init_features):
+    test_case.assertIsInstance(init_features, InitFeatures)
+    assert_feature_helpers_return_bool(test_case, init_features)
+    test_case.assertIsInstance(init_features.initial_routing_sync(), bool)
+
+
 
 class TestLdkNode(unittest.TestCase):
     def setUp(self):
@@ -153,6 +176,10 @@ def test_channel_full_cycle(self):
         node_id_2 = node_2.node_id()
         print("Node ID 2:", node_id_2)
 
+        # Check node-announcement features exposed through NodeStatus.
+        for node in [node_1, node_2]:
+            node_features_exposed(self, node.status().node_features)
+
         address_1 = node_1.onchain_payment().new_address()
         txid_1 = send_to_address(address_1, 100000)
         address_2 = node_2.onchain_payment().new_address()
@@ -200,6 +227,10 @@ def test_channel_full_cycle(self):
 
         channel_ready_event_2 = expect_event(node_2, Event.CHANNEL_READY)
 
+        # Check negotiated init features exposed through ChannelDetails.
+        for channel in [node_1.list_channels()[0], node_2.list_channels()[0]]:
+            init_features_exposed(self, channel.counterparty.features)
+
         description = Bolt11InvoiceDescription.DIRECT("asdf")
         invoice = node_2.bolt11_payment().receive(2500000, description, 9217)
         node_1.bolt11_payment().send(invoice, None)