Document P2P TLS support for private cloud

qdrant-landing/content/documentation/private-cloud/qdrant-cluster-management.md

@@ -139,7 +139,7 @@ spec:
 
 If you set the `jwt_rbac` flag, you will also be able to create granular [JWT tokens for role based access control](/documentation/guides/security/#granular-access-control-with-jwt).
 
-### Configuring TLS
+### Configuring TLS for Database Access
 
 If you want to configure TLS for accessing your Qdrant database, there are two options:
 
@@ -195,3 +195,92 @@ spec:
           name: qdrant-tls
           key: tls.key
 ```
+
+### Configuring TLS for Inter-cluster Communication
+
+*Available as of Operator v2.2.0*
+
+If you want to encrypt communication between Qdrant nodes, you need to enable TLS by providing
+certificate, key, and root CA certificate used for generating the former.
+
+Similar to the instruction stated in the previous section, you need to create a secret:
+
+```shell
+ kubectl create secret generic qdrant-p2p-tls \
+        --from-file=tls.crt=qdrant-nodes.crt \
+        --from-file=tls.key=qdrant-nodes.key \
+        --from-file=ca.crt=root-ca.crt
+        --namespace the-qdrant-namespace
+```
+
+The resulting secret will look like this:
+
+```yaml
+apiVersion: v1
+data:
+  tls.crt: ...
+  tls.key: ...
+  ca.crt: ...
+kind: Secret
+metadata:
+  name: qdrant-p2p-tls
+  namespace: the-qdrant-namespace
+type: Opaque
+```
+You can reference the secret in the QdrantCluster spec:
+
+```yaml
+apiVersion: qdrant.io/v1
+kind: QdrantCluster
+metadata:
+  name: test-cluster
+  labels:
+    cluster-id: "my-cluster"
+    customer-id: "acme-industries"
+spec:
+  id: "my-cluster"
+  version: "v1.13.3"
+  size: 2
+  resources:
+    cpu: 100m
+    memory: "1Gi"
+    storage: "2Gi"
+  config:
+    service:
+      enable_tls: true
+    tls:
+      caCert:
+        secretKeyRef:
+          name: qdrant-p2p-tls
+          key: ca.crt
+      cert:
+        secretKeyRef:
+          name: qdrant-p2p-tls
+          key: tls.crt
+      key:
+        secretKeyRef:
+          name: qdrant-p2p-tls
+          key: tls.key
+```
+
+<aside role="status">
+The operator assigns the names to nodes in cluster according to the following convention:
+
+```
+qdrant-{spec.id}-{node-index}.qdrant-headless-{spec.id}
+```
+
+Therefore, in addition to the domain used for accessing the database, 
+the provided certificate must contain Subjective Alternative Names (SAN) for all foreseen nodes.
+It can be created with a tool of your choice, e.g., 
+using [step CLI](https://smallstep.com/docs/step-cli/installation/).
+Following the example `QdrantCluster`, the proper certificate can be obtained with:
+
+```shell
+step certificate create mydomain.com qdrant-nodes.crt qdrant-nodes.key \
+  --profile leaf --not-after 43800h \
+  --ca root-ca.crt --ca-key root-ca.key \
+  --san qdrant-my-cluster-0.qdrant-headless-my-cluster \
+  --san qdrant-my-cluster-1.qdrant-headless-my-cluster
+```
+</aside>