fix: allow http MX delivery to carry max-message-sized messages

it otherwise uses the 1MB nginx default body size,
forcing a fallback to SMTP (which if not available, fails the delivery)

Author: hpk42

cmdeploy/src/cmdeploy/nginx/nginx.conf.j2

@@ -75,6 +75,7 @@ http {
 		server_name {{ config.mail_domain }} mta-sts.{{ config.mail_domain }};
 
 		location /mxdeliv {
+		    client_max_body_size {{ config.max_message_size }};
 		    proxy_pass http://127.0.0.1:{{ config.filtermail_http_port_incoming }};
 		}
 

cmdeploy/src/cmdeploy/tests/online/test_1_basic.py

@@ -5,6 +5,7 @@
 import time
 
 import pytest
+import requests
 from chatmaild.config import is_valid_ipv4
 
 from cmdeploy import remote
@@ -326,3 +327,14 @@ def test_nginx_access_log_only_defined_once(sshdomain):
     assert len(access_logs) == 1, (
         f"expected 1 access_log, found {len(access_logs)}: {access_logs}"
     )
+
+
+@pytest.mark.filterwarnings("ignore::urllib3.exceptions.InsecureRequestWarning")
+def test_mxdeliv_respects_max_message_size(maildomain, chatmail_config):
+    url = f"https://{maildomain}/mxdeliv"
+    verify = chatmail_config.tls_cert_mode == "acme"
+    size = chatmail_config.max_message_size
+    res = requests.post(url, data=b"x" * size, verify=verify)
+    assert res.text == "500 Invalid DATA"
+    res = requests.post(url, data=b"x" * (size + 1), verify=verify)
+    assert res.status_code == 413