* found, the existing values are replaced.
 */
internal fun Headers.Builder.commonSet(
  name: String,
  value: String,
) = apply {
  headersCheckName(name)
  headersCheckValue(value, name)
  removeAll(name)
  commonAddLenient(name, value)
}

/** Equivalent to `build().get(name)`, but potentially faster. */
internal fun Headers.Builder.commonGet(name: String): String? {
  for (i in namesAndValues.size - 2 downTo 0 step 2) {