gh-67041: Allow to distinguish between empty and not defined URI components (GH-123305)

Changes in the urllib.parse module:

* Add option missing_as_none in urlparse(), urlsplit() and urldefrag(). If
  it is true, represent not defined components as None instead of an
  empty string.
* Add option keep_empty in urlunparse() and urlunsplit(). If it is
  true, keep empty non-None components in the resulting string.

Author: serhiy-storchaka

Doc/library/urllib.parse.rst

@@ -836,6 +836,18 @@ unittest
   (Contributed by Garry Cairns in :gh:`134567`.)
 
 
+urllib.parse
+------------
+
+* Add the *missing_as_none* parameter to :func:`~urllib.parse.urlparse`,
+  :func:`~urllib.parse.urlsplit` and :func:`~urllib.parse.urldefrag` functions.
+  Add the *keep_empty* parameter to :func:`~urllib.parse.urlunparse` and
+  :func:`~urllib.parse.urlunsplit` functions.
+  This allows to distinguish between empty and not defined URI components
+  and preserve empty components.
+  (Contributed by Serhiy Storchaka in :gh:`67041`.)
+
+
 venv
 ----