Proxito: inject hosting integration header for build.commands (readthedocs#10219)

* Proxito: inject hosting integration header for `build.commands`

Versions using `build.commands` will start using the new Read the Docs
JavaScript client.

This is still under beta testing, but we want to move forward slowly and start
exposing these features to projects that don't have access currently.

Related readthedocs/addons#26

* Proxito: check if the version exists first

Author: humitos

readthedocs/proxito/middleware.py

@@ -281,11 +281,22 @@ def process_request(self, request):  # noqa
 
     def add_hosting_integrations_headers(self, request, response):
         project_slug = getattr(request, "path_project_slug", "")
+        version_slug = getattr(request, "path_version_slug", "")
+
         if project_slug:
             project = Project.objects.get(slug=project_slug)
             if project.has_feature(Feature.HOSTING_INTEGRATIONS):
                 response["X-RTD-Hosting-Integrations"] = "true"
 
+            # Inject the new integrations for versions using `build.commands`
+            version = project.versions.filter(slug=version_slug).first()
+            if (
+                version
+                and version.config
+                and version.config.get("build", {}).get("commands", {}) != []
+            ):
+                response["X-RTD-Hosting-Integrations"] = "true"
+
     def process_response(self, request, response):  # noqa
         self.add_proxito_headers(request, response)
         self.add_cache_headers(request, response)