add smtp module and testing

tests/test_config.py

@@ -53,3 +53,25 @@ def test_settings_derive_development_ticktick_redirect_uri(monkeypatch) -> None:
 
     assert settings.app_base_url == "http://localhost:11001"
     assert settings.ticktick_redirect_uri == "http://localhost:11001/ticktick/auth/code"
+
+
+def test_settings_support_smtp_fields(monkeypatch) -> None:
+    monkeypatch.setenv("SMTP_ENABLED", "true")
+    monkeypatch.setenv("SMTP_HOST", "smtp.example.com")
+    monkeypatch.setenv("SMTP_PORT", "2525")
+    monkeypatch.setenv("SMTP_USERNAME", "smtp-user")
+    monkeypatch.setenv("SMTP_PASSWORD", "smtp-password")
+    monkeypatch.setenv("SMTP_FROM_ADDRESS", "sender@example.com")
+    monkeypatch.setenv("SMTP_TO_ADDRESS", "recipient@example.com")
+    monkeypatch.setenv("SMTP_USE_STARTTLS", "false")
+
+    settings = Settings(_env_file=None)
+
+    assert settings.smtp_enabled is True
+    assert settings.smtp_host == "smtp.example.com"
+    assert settings.smtp_port == 2525
+    assert settings.smtp_username == "smtp-user"
+    assert settings.smtp_password == "smtp-password"
+    assert settings.smtp_from_address == "sender@example.com"
+    assert settings.smtp_to_address == "recipient@example.com"
+    assert settings.smtp_use_starttls is False