*
 * @throws IllegalArgumentException if this is not a well-formed media type.
 */
internal fun String.commonToMediaType(): MediaType {
  val typeSubtype: MatchResult =
    TYPE_SUBTYPE.matchAtPolyfill(this, 0)
      ?: throw IllegalArgumentException("No subtype found for: \"$this\"")
  val type = typeSubtype.groupValues[1].lowercase()
  val subtype = typeSubtype.groupValues[2].lowercase()