Finally! We can now stop editing manually our crds definition. Simply
run `make crds-gen`. These two files:
* `cluster/examples/kubernetes/ceph/crds.yaml`
* `cluster/charts/rook-ceph/templates/resources.yaml`
will be autogenerated for us.
We rely on the controller-gen tool, it reads our API definitions from
`pkg/apis/` and produces the CRD files accordingly.
It uses "markers" to add extra yaml fields to the CRD, for instance we
have a lot fields with:
```
nullable: true
x-kubernetes-preserve-unknown-fields: true
```
The corresponding API type markers are:
```
// +kubebuilder:pruning:PreserveUnknownFields
// +nullable
```
For more API convention see
https://github.com/kubernetes/community/blob/master/contributors/devel/sig-architecture/api-conventions.md#optional-vs-required
and for the markers see: https://book.kubebuilder.io/reference/markers/crd-validation.html
Signed-off-by: Sébastien Han <seb@redhat.com>