Fix InspIRCd UID and message-tag parsing; add irctest controller

The UID introduction omitted the second user field (insp sends both a real and a
displayed user), and the parser didn't strip IRCv3 message-tag prefixes, so
tagged PRIVMSGs addressed to a service were dropped. With both fixed a service
links to a real insp4 uplink and answers commands. Adds an irctest services
controller so this is verified against an isolated, throwaway ircd.

testing/fedserv_services.py

@@ -0,0 +1,57 @@
+"""irctest controller for fedserv.
+
+Copy (or symlink) this file into irctest's ``irctest/controllers/`` directory,
+then run the services tests against an isolated InspIRCd + fedserv:
+
+    FEDSERV_BIN=/path/to/federated-services/target/release/fedserv \\
+    PATH=/path/to/inspircd/run/bin:$PATH \\
+    python -m pytest \\
+        --controller=irctest.controllers.inspircd \\
+        --services-controller=irctest.controllers.fedserv_services \\
+        irctest/server_tests/account_registration.py
+
+irctest spawns its own ircd + services on random ports, so this never touches a
+real network. See https://github.com/progval/irctest
+"""
+import os
+import shutil
+from typing import Type
+
+from irctest.basecontrollers import BaseServicesController, DirectoryBasedController
+
+CONFIG = """\
+[uplink]
+host = "{server_hostname}"
+port = {server_port}
+password = "password"
+
+[server]
+name = "My.Little.Services"
+sid = "42S"
+description = "Federated Services"
+protocol = 1206
+"""
+
+
+class FedservController(BaseServicesController, DirectoryBasedController):
+    software_name = "fedserv"
+    saslserv = "NickServ"
+
+    def run(self, protocol: str, server_hostname: str, server_port: int) -> None:
+        self.create_config()
+        assert protocol in ("inspircd", "inspircd3"), f"fedserv speaks inspircd, not {protocol}"
+
+        binary = (
+            os.environ.get("FEDSERV_BIN")
+            or shutil.which("fedserv")
+            or "target/release/fedserv"
+        )
+
+        with self.open_file("config.toml") as fd:
+            fd.write(CONFIG.format(server_hostname=server_hostname, server_port=server_port))
+
+        self.proc = self.execute([binary, "config.toml"], cwd=self.directory)
+
+
+def get_irctest_controller_class() -> Type[FedservController]:
+    return FedservController