feat: funciones email SMTP en Python (infra)

smtp_send: conecta+envia+cierra en un paso via smtplib (TLS/STARTTLS/plain).
email_build_html: construye EmailMessagePy frozen dataclass con cuerpo HTML.
Solo stdlib Python: smtplib, email.mime. Tests con mock SMTP server threading.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

python/functions/infra/smtp_send_test.py

@@ -0,0 +1,149 @@
+"""Tests para smtp_send usando un mock SMTP server con smtpd/aiosmtpd o threading."""
+
+import smtplib
+import socket
+import sys
+import os
+import threading
+import time
+from io import StringIO
+
+sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
+
+from infra.smtp_send import smtp_send, SMTPConfigPy, EmailAttachmentPy
+
+
+def _find_free_port() -> int:
+    """Encuentra un puerto libre en 127.0.0.1."""
+    with socket.socket() as s:
+        s.bind(("127.0.0.1", 0))
+        return s.getsockname()[1]
+
+
+class _MockSMTPHandler:
+    """Handler de conexion SMTP minimal para tests."""
+
+    def __init__(self, conn: socket.socket):
+        self.conn = conn
+
+    def run(self):
+        f = self.conn.makefile("rb")
+        try:
+            self._send(b"220 mock SMTP\r\n")
+            while True:
+                line = f.readline()
+                if not line:
+                    break
+                cmd = line.decode("utf-8", errors="replace").strip().upper()
+                if cmd.startswith("EHLO") or cmd.startswith("HELO"):
+                    self._send(b"250 mock\r\n")
+                elif cmd.startswith("MAIL FROM"):
+                    self._send(b"250 OK\r\n")
+                elif cmd.startswith("RCPT TO"):
+                    self._send(b"250 OK\r\n")
+                elif cmd.startswith("DATA"):
+                    self._send(b"354 End with .\r\n")
+                    while True:
+                        dl = f.readline()
+                        if dl.strip() == b".":
+                            break
+                    self._send(b"250 OK\r\n")
+                elif cmd.startswith("QUIT"):
+                    self._send(b"221 Bye\r\n")
+                    break
+                else:
+                    self._send(b"502 Not recognized\r\n")
+        finally:
+            self.conn.close()
+
+    def _send(self, data: bytes):
+        self.conn.sendall(data)
+
+
+class _MockSMTPServer:
+    """SMTP server minimal corriendo en thread para tests."""
+
+    def __init__(self):
+        self.port = _find_free_port()
+        self._sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        self._sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        self._sock.bind(("127.0.0.1", self.port))
+        self._sock.listen(5)
+        self._sock.settimeout(2.0)
+        self._stop = threading.Event()
+        self._thread = threading.Thread(target=self._serve, daemon=True)
+
+    def start(self):
+        self._thread.start()
+        return self
+
+    def stop(self):
+        self._stop.set()
+        self._sock.close()
+
+    def _serve(self):
+        while not self._stop.is_set():
+            try:
+                conn, _ = self._sock.accept()
+                t = threading.Thread(target=_MockSMTPHandler(conn).run, daemon=True)
+                t.start()
+            except OSError:
+                break
+
+    def cfg(self) -> SMTPConfigPy:
+        return SMTPConfigPy(host="127.0.0.1", port=self.port, tls_mode="")
+
+
+def test_envia_texto_plano_via_mock_smtpd():
+    srv = _MockSMTPServer().start()
+    try:
+        smtp_send(
+            srv.cfg(),
+            from_addr="alice@example.com",
+            to=["bob@example.com"],
+            subject="Test plain",
+            body_text="Hello Bob",
+        )
+    finally:
+        srv.stop()
+
+
+def test_envia_html_via_mock_smtpd():
+    srv = _MockSMTPServer().start()
+    try:
+        smtp_send(
+            srv.cfg(),
+            from_addr="alice@example.com",
+            to=["bob@example.com"],
+            subject="Test HTML",
+            body_html="<b>Hello</b>",
+        )
+    finally:
+        srv.stop()
+
+
+def test_envia_con_adjunto_via_mock_smtpd():
+    srv = _MockSMTPServer().start()
+    try:
+        att = EmailAttachmentPy(filename="f.txt", content_type="text/plain", data=b"file data")
+        smtp_send(
+            srv.cfg(),
+            from_addr="alice@example.com",
+            to=["bob@example.com"],
+            subject="Test attachment",
+            body_text="See attachment",
+            attachments=[att],
+        )
+    finally:
+        srv.stop()
+
+
+def test_error_si_host_no_existe():
+    port = _find_free_port()
+    # Port is free but nothing listens — should get connection refused
+    cfg = SMTPConfigPy(host="127.0.0.1", port=port, tls_mode="")
+    try:
+        smtp_send(cfg, "a@x.com", ["b@x.com"], "sub", body_text="hi")
+        assert False, "Expected RuntimeError"
+    except RuntimeError:
+        pass