First step to fix nested urls.py files.

This patch accumulates parent_regexps with the current one, but changes the ABI, so there's a second patch to come to fix `ApiEndpoint`

Author: StyXman

rest_framework_docs/api_docs.py

@@ -21,13 +21,13 @@ def __init__(self, drf_router=None):
         else:
             self.get_all_view_names(root_urlconf.urlpatterns)
 
-    def get_all_view_names(self, urlpatterns, parent_pattern=None):
+    def get_all_view_names(self, urlpatterns, parent_regex=None):
         for pattern in urlpatterns:
             if isinstance(pattern, RegexURLResolver):
-                parent_pattern = None if pattern._regex == "^" else pattern
-                self.get_all_view_names(urlpatterns=pattern.url_patterns, parent_pattern=parent_pattern)
+                regex = '' if pattern._regex == "^" else pattern._regex
+                self.get_all_view_names(urlpatterns=pattern.url_patterns, parent_regex=parent_regex+regex)
             elif isinstance(pattern, RegexURLPattern) and self._is_drf_view(pattern) and not self._is_format_endpoint(pattern):
-                api_endpoint = ApiEndpoint(pattern, parent_pattern, self.drf_router)
+                api_endpoint = ApiEndpoint(pattern, parent_regex, self.drf_router)
                 self.endpoints.append(api_endpoint)
 
     def _is_drf_view(self, pattern):