parseQueryParamsDecoded

Parse a query string into key/value pairs with optional form-style decoding.

Performs the same splitting semantics as parseQueryParams, then applies:

• If plusAsSpace is true, maps `+` to space (U+0020) before percent-decoding, emulating application/x-www-form-urlencoded behavior.
• Percent-decodes %HH escapes in both keys and values using pctDecode.

  Parameters

  q	Query string without the leading `?`.
  plusAsSpace	If true, interpret `+` as space prior to decoding.

  Returns

  Array of decoded (key, value) tuples.

  Examples

  import std.typecons : tuple;
  auto p1 = parseQueryParamsDecoded("q=hello%20world", false);
  assert(p1[0] == tuple("q", "hello world"));
  
  auto p2 = parseQueryParamsDecoded("q=hello+world+%2B&u=%E2%82%AC", true);
  assert(p2[0] == tuple("q", "hello world +"));
  assert(p2[1] == tuple("u", "€"));