Web: add support for the POST HTTP method. (#1097)

* Web: add support for the POST HTTP method.

This patch adds support for POST in addition to the already supported GET.

This is needed for implementing more complex web modules that also
support configuration modifications and advanced queries.

* Base web: return METHOD_NOT_ALLOWED when method isn't implemenetd.

Co-authored-by: Unrud <Unrud@users.noreply.github.com>

radicale/web/__init__.py

@@ -21,7 +21,7 @@ Take a look at the class ``BaseWeb`` if you want to implement your own.
 
 """
 
-from radicale import utils
+from radicale import httputils, utils
 
 INTERNAL_TYPES = ("none", "internal")
 
@@ -52,4 +52,16 @@ class BaseWeb:
         ``user`` is empty for anonymous users.
 
         """
-        raise NotImplementedError
+        return httputils.METHOD_NOT_ALLOWED
+
+    def post(self, environ, base_prefix, path, user):
+        """POST request.
+
+        ``base_prefix`` is sanitized and never ends with "/".
+
+        ``path`` is sanitized and always starts with "/.web"
+
+        ``user`` is empty for anonymous users.
+
+        """
+        return httputils.METHOD_NOT_ALLOWED