fix: match actor DNS names case-insensitively at the router

[Mesut Oezdil (mesutoezdil)]

DNS lookups are case-insensitive (RFC 4343), so a client that resolves MyActor.MySpace.actors.resources.substrate.ate.dev reaches the router with that spelling preserved in Host/:authority (Go's http.Client and curl -H both send the host as written). ParseActorDNSName compared it byte for byte against a strictly lower-case suffix and name pattern, so the request was rejected with a 404 by invalidHostErr even though its DNS lookup had resolved to that very actor.

Fold the name to lower case before parsing. Actor and atespace names are always lower case (ResourceNameRegexPattern), so a folded name either addresses the same actor its lookup resolved to, or fails validation exactly as before.

[Eitan Yarmush (EItanya)]

Optional note (AI-generated):

K and K look the same, but they are different characters. K is the Unicode Kelvin sign (U+212A), while K is the ASCII letter K (U+004B).

Go converts K to the ASCII letter k when calling strings.ToLower. As a result, a malformed non-ASCII hostname could become a valid hostname during parsing and be routed to the wrong actor.

Consider either rejecting non-ASCII hostnames before lowercasing or lowercasing only ASCII letters A-Z. If an earlier layer already guarantees that hostnames are ASCII, no change may be needed here; this would be defense in depth.

[Mesut Oezdil (mesutoezdil)]

Optional note (AI-generated):

K and K look the same, but they are different characters. K is the Unicode Kelvin sign (U+212A), while K is the ASCII letter K (U+004B).

Go converts K to the ASCII letter k when calling strings.ToLower. As a result, a malformed non-ASCII hostname could become a valid hostname during parsing and be routed to the wrong actor.

Consider either rejecting non-ASCII hostnames before lowercasing or lowercasing only ASCII letters A-Z. If an earlier layer already guarantees that hostnames are ASCII, no change may be needed here; this would be defense in depth.

hm, oki makes sense, i did, ptal