Addons: default "Include subprojects" to true on search (#12278)

Initial small approach to make the "Include subprojects" filter enabled
by default. I'm adding a new field to the search filter to communicate
if it's enabled or disabled by default. This value will be able to be
changed by the user in the future from the project admin settings.

* Related readthedocs/addons#22

Author: humitos

readthedocs/proxito/views/hosting.py

@@ -545,6 +545,7 @@ def _v1(self, project, version, build, filename, url, request):
                     [
                         "Include subprojects",
                         f"subprojects:{project.slug}/{version.slug}",
+                        True,
                     ]
                 )
             elif project.superprojects.exists():
@@ -553,6 +554,7 @@ def _v1(self, project, version, build, filename, url, request):
                     [
                         "Include subprojects",
                         f"subprojects:{superproject.slug}/{version.slug}",
+                        True,
                     ]
                 )