Inbound Email

SendGrid Inbound Parse target (multipart/form-data in production; urlencoded form or JSON also accepted -- the parsing below is content- type agnostic once the fields are a str-keyed mapping). Always returns 200 on a well-formed webhook POST, even when the email itself could not be turned into a ticket (dead_lettered=true in the body) -- a non-200 here would make SendGrid retry-storm a request that already succeeded at the one thing that matters, durably recording the attempt.