private val QUOTED_STRING_DELIMITERS = "\"\\".encodeUtf8()
private val TOKEN_DELIMITERS = "\t ,=".encodeUtf8()

/**
 * Parse RFC 7235 challenges. This is awkward because we need to look ahead to know how to
 * interpret a token.
 *
 * For example, the first line has a parameter name/value pair and the second line has a single
 * token68:
 *
 * ```
 * WWW-Authenticate: Digest foo=bar

FDFC          ; mapped                 ; 0631 06CC 0627 0644 #3.2 RIAL SIGN
FDFD          ; valid                  ;      ; NV8    # 4.0  ARABIC LIGATURE BISMILLAH AR-RAHMAN AR-RAHEEM
FDFE..FDFF    ; valid                  ;      ; NV8    # 14.0 ARABIC LIGATURE SUBHAANAHU WA TAAALAA..ARABIC LIGATURE AZZA WA JALL