Add project: skip config step if YAML file is present (#11540)

* Add project: skip config step if YAML file is present

This commit checks if the repository contains a `.readthedocs.yaml` testing
different possible names, and skip the "Add a configuration file to your
project" setp if it's present.

It only works for GitHub for now, but we can probably add GitLab as well.

Related readthedocs/ext-theme#445

* Show a Django message if we detected a .yaml file

* Use OAuth session to support YAML check on private repositories

* Update readthedocs/projects/views/private.py

Co-authored-by: Anthony <[email protected]>

* Logging filename

* Typo

---------

Co-authored-by: Anthony <[email protected]>

Author: humitos

readthedocs/projects/views/private.py

@@ -49,7 +49,8 @@
 from readthedocs.integrations.models import HttpExchange, Integration
 from readthedocs.invitations.models import Invitation
 from readthedocs.notifications.models import Notification
-from readthedocs.oauth.services import registry
+from readthedocs.oauth.constants import GITHUB
+from readthedocs.oauth.services import GitHubService, registry
 from readthedocs.oauth.tasks import attach_webhook
 from readthedocs.oauth.utils import update_webhook
 from readthedocs.projects.filters import ProjectListFilterSet
@@ -347,7 +348,57 @@ def get_form_kwargs(self, step=None):
 
     def get_template_names(self):
         """Return template names based on step name."""
-        return "projects/import_{}.html".format(self.steps.current)
+        return f"projects/import_{self.steps.current}.html"
+
+    def process_step(self, form):
+        # pylint: disable=too-many-nested-blocks
+        if isinstance(form, ProjectBasicsForm):
+            remote_repository = form.cleaned_data.get("remote_repository")
+            if remote_repository and remote_repository.vcs_provider == GITHUB:
+                remote_repository_relations = (
+                    remote_repository.remote_repository_relations.filter(
+                        user=self.request.user,
+                        account__isnull=False,
+                    )
+                    .select_related("account", "user")
+                    .only("user", "account")
+                )
+                for relation in remote_repository_relations:
+                    service = GitHubService(relation.user, relation.account)
+                    session = service.get_session()
+
+                    for yaml in [
+                        ".readthedocs.yaml",
+                        ".readthedocs.yml",
+                        "readthedocs.yaml",
+                        "readthedocs.yml",
+                    ]:
+                        try:
+                            response = session.head(
+                                f"https://api.github.com/repos/{remote_repository.full_name}/contents/{yaml}",
+                                timeout=1,
+                            )
+                            if response.ok:
+                                log.info(
+                                    "Read the Docs YAML file found for this repository.",
+                                    filename=yaml,
+                                )
+                                messages.success(
+                                    self.request,
+                                    _(
+                                        "We detected a configuration file in your repository and started your project's first build."
+                                    ),
+                                )
+                                self.form_list.pop("config")
+                                break
+                        except Exception:
+                            log.warning(
+                                "Failed when hitting GitHub API to check for .readthedocs.yaml file.",
+                                filename=yaml,
+                            )
+                            continue
+
+        return super().process_step(form)
 
     def done(self, form_list, **kwargs):
         """