✨ Quickstart: Add note about editing the resource

If you follow the guide from top to `kubectl apply -k config/samples/`,
then the command will fail here.

I added a note, so that the first-time-user
experience is a bit more convenient.

Author: guettli

docs/book/src/quick-start.md

@@ -183,13 +183,35 @@ make run
 
 ## Install Instances of Custom Resources
 
-If you pressed `y` for Create Resource [y/n] then you created a CR for your CRD in your samples (make sure to edit them first if you've changed the
-API definition):
+If you pressed `y` for Create Resource [y/n] then you created a CR for your CRD in your
+`config/samples/` directory.
+
+Edit `config/samples/webapp_v1_guestbook.yaml` to contain a valid `spec`. For example:
+
+```yaml
+# ...
+spec:
+  foo: bar
+```
+
+Hint: "foo" is a string field defined in `api/v1/guestbook_types.go`:
+
+```go
+// foo is an example field of Guestbook. Edit guestbook_types.go to remove/update
+// +optional
+Foo *string `json:"foo,omitempty"`
+```
 
 ```bash
 kubectl apply -k config/samples/
 ```
 
+You can have a look at your applied resource now:
+
+```bash
+kubectl get guestbooks.webapp.my.domain guestbook-sample -o yaml
+```
+
 ## Run It On the Cluster
 
 When your controller is ready to be packaged and tested in other clusters.
@@ -313,4 +335,4 @@ before designing your own API and project.
 [markers]: reference/markers.md
 [controller-gen]: https://sigs.k8s.io/controller-tools/cmd/controller-gen
 [scaffolding-markers]: reference/markers/scaffold.md
-[ai-gh-models]: https://docs.github.com/en/github-models/about-github-models
+[ai-gh-models]: https://docs.github.com/en/github-models/about-github-models