Swaps over Nostr

- Separation between SwapManager and its transport:
   Legacy transpport uses http, Nostr uses websockets
 - The transport uses a context to open/close connections.
   This context is not async, because it needs to be called
   from the GUI
 - Swapserver fees values are initialized to None instead
   of 0, so that any attempt to use them before the swap
   manager is initialized will raise an exception.
 - Remove swapserver fees disk caching (swap_pairs file)
 - Regtests use http transport
 - Android uses http transport (until QML is ready)

tests/regtest.py

@@ -79,10 +79,14 @@ class TestLightningSwapserver(TestLightning):
     agents = {
         'alice': {
             'use_gossip': 'false',
+            'swapserver_url': 'http://localhost:5455',
+            'nostr_relays': "''",
         },
         'bob': {
             'lightning_listen': 'localhost:9735',
             'enable_plugin_swapserver': 'true',
+            'swapserver_port': '5455',
+            'nostr_relays': "''",
         }
     }
 

tests/test_simple_config.py

@@ -148,22 +148,6 @@ class Test_SimpleConfig(ElectrumTestCase):
         config.NETWORK_MAX_INCOMING_MSG_SIZE = None
         self.assertEqual(MAX_MSG_SIZE_DEFAULT, config.NETWORK_MAX_INCOMING_MSG_SIZE)
 
-    def test_configvars_get_default_value_complex_fn(self):
-        config = SimpleConfig(self.options)
-        self.assertEqual("https://swaps.electrum.org/api", config.SWAPSERVER_URL)
-
-        config.SWAPSERVER_URL = "http://localhost:9999"
-        self.assertEqual("http://localhost:9999", config.SWAPSERVER_URL)
-
-        config.SWAPSERVER_URL = None
-        self.assertEqual("https://swaps.electrum.org/api", config.SWAPSERVER_URL)
-
-        constants.BitcoinTestnet.set_as_network()
-        try:
-            self.assertEqual("https://swaps.electrum.org/testnet", config.SWAPSERVER_URL)
-        finally:
-            constants.BitcoinMainnet.set_as_network()
-
     def test_configvars_convert_getter(self):
         config = SimpleConfig(self.options)
         self.assertEqual(None, config.NETWORK_PROXY)