A value that goes into an HTTP header (userAgent, defaultHeaders): not blank,
no C0 control character except tab, no DEL, and nothing above U+00FF. Node's
HTTP layer would otherwise throw an opaque "Invalid character in header content"
at request time (a CR/LF could split the header). Checked by char code so the
source stays free of control bytes.
A value that goes into an HTTP header (
userAgent,defaultHeaders): not blank, no C0 control character except tab, no DEL, and nothing above U+00FF. Node's HTTP layer would otherwise throw an opaque "Invalid character in header content" at request time (a CR/LF could split the header). Checked by char code so the source stays free of control bytes.