fix: add missing doc.go for proper groupName inference

Most go code generators such as kube-openapi rely on gengo [1] to infer the
annotated tags.
When dealing with package annotations, gengo extracts them from
the doc.go file [2].

The types defined in apis/metal3.io/v1alpha1 do have a package annotated
with +groupName. However, the annotation is in the groupversion_info.go
file instead.

You can see comments that refer to this issue [3] [4]

[1] https://github.com/kubernetes/gengo/
[2] https://github.com/kubernetes/gengo/blob/2b36238f13e9b8aebe4c286c2ffb2fc71f4be3c5/types/types.go#L121-L126
[3] kubernetes/code-generator#150 (comment)
[4] kubernetes/code-generator#135

Signed-off-by: Marc Nuri <[email protected]>

apis/metal3.io/v1alpha1/doc.go

@@ -0,0 +1,19 @@
+/*
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package v1alpha1 contains API Schema definitions for the metal3.io v1alpha1 API group
+// +kubebuilder:object:generate=true
+// +groupName=metal3.io
+package v1alpha1