Http headers do not use the formatting you show.
https://datatracker.ietf.org/doc/html/rfc2616#section-4.2
https://en.wikipedia.org/wiki/List_of_HTTP_header_fields
Quote
Header fields are colon-separated key-value pairs in clear-text string format, terminated by a carriage return (CR) and line feed (LF) character sequence.

More like this:
Code
"key1:value1\r\nkey2:value2\r\nkey3:value3"