Group API reference docs

Author: fabriziopandini

docs/book/src/SUMMARY.md

@@ -105,10 +105,12 @@
           - [Webhooks](./developer/providers/webhooks.md)
           - [Controllers and Reconciliation](./developer/providers/implementers-guide/controllers_and_reconciliation.md)
           - [Building, Running, Testing](./developer/providers/implementers-guide/building_running_and_testing.md)
-    - [CustomResourceDefinitions relationships](./developer/crd-relationships.md)
 - [Troubleshooting](./user/troubleshooting.md)
 - [Reference](./reference/reference.md)
-    - [API Reference](./reference/api_reference.md)
+    - [API Reference](./reference/api/reference.md)
+      - [Labels and Annotations](reference/api/labels-and-annotations.md)
+      - [CRD relationships](reference/api/crd-relationships.md)
+      - [Owner References](reference/api/owner-references.md)
     - [Glossary](./reference/glossary.md)
     - [Provider List](./reference/providers.md)
     - [Ports](./reference/ports.md)
@@ -117,5 +119,3 @@
     - [Jobs](./reference/jobs.md)
     - [Code Review in Cluster API](./REVIEWING.md)
     - [Version Support](./reference/versions.md)
-    - [Supported Labels and Annotations](./reference/labels_and_annotations.md)
-    - [Owner References](./reference/owner_references.md)

docs/book/src/developer/crd-relationships.md renamed to docs/book/src/reference/api/crd-relationships.md

@@ -14,8 +14,8 @@ The direction of the arrows indicates the direction of "management" or "referenc
 
 ## Control plane machines relationships
 
-![]( ../images/kubeadm-control-plane-machines-resources.png)
+![]( ../../images/kubeadm-control-plane-machines-resources.png)
 
 ## Worker machines relationships
 
-![]( ../images/worker-machines-resources.png)
+![]( ../../images/worker-machines-resources.png)