update

redirect/root-to-www.conf

@@ -1,9 +1,14 @@
 set $root_domain "";
 
+# Derive the apex domain from a www-prefixed primary server_name. This keeps the
+# snippet simple, but it also means callers should not use it on multi-name
+# server blocks whose first name is not the canonical www host.
 if ($server_name ~* ^www\.(?<apex_domain>.+)$) {
 	set $root_domain $apex_domain;
 }
 
+# Use 307 so POST and other non-GET methods keep their method during
+# canonicalization instead of being rewritten to GET as with many 301/302 flows.
 if ($host = $root_domain) {
 	return 307 $scheme://$server_name$request_uri;
 }