docs: Document the annotation "secrets.stackable.tech/backend.autotls.cert.domain-components-in-subject-dn"

Author: siegfriedweber

docs/modules/secret-operator/pages/volume.adoc

@@ -166,6 +166,36 @@ For example, given a requested lifetime of 1 day and a jitter factor of 0.2, the
 
 Jittering may be disabled by setting the jitter factor to 0.
 
+=== `secrets.stackable.tech/backend.autotls.cert.domain-components-in-subject-dn`
+
+*Required*: false
+
+*Default value*: `"false"`
+
+*Backends*: xref:secretclass.adoc#backend-autotls[]
+
+If set to `"true"`, the domain components of the Pod's fully qualified domain name (FQDN) are appended to the subject distinguished name (DN) of the TLS certificate.
+
+For example, the subject DN could look as follows:
+
+```
+CN=generated certificate for pod, DC=my-pod-0, DC=my-statefulset-service, DC=my-namespace, DC=svc, DC=cluster, DC=local
+```
+
+[NOTE]
+====
+Many products use the string representation of distinguished names as described in https://www.ietf.org/rfc/rfc4514.txt[RFC 4514{external-link-icon}^].
+The string representation starts with the last element of the sequence and moving backwards toward the first.
+
+The example above becomes:
+
+```
+DC=local,DC=cluster,DC=svc,DC=my-namespace,DC=my-statefulset-service,DC=my-pod-0,CN=generated certificate for pod
+```
+
+Attribute names can be in upper or lower case, with or without spaces between them.
+====
+
 === `secrets.stackable.tech/backend.cert-manager.cert.lifetime`
 
 *Required*: false

rust/operator-binary/src/backend/mod.rs

@@ -129,6 +129,12 @@ pub struct SecretVolumeSelector {
     )]
     pub autotls_cert_jitter_factor: f64,
 
+    /// If set to `"true"`, the domain components of the Pod's fully qualified domain name (FQDN)
+    /// are appended to the subject distinguished name (DN) of the TLS certificate.
+    ///
+    /// For example, the subject DN could look as follows:
+    ///
+    /// `CN=generated certificate for pod, DC=my-pod-0, DC=my-statefulset-service, DC=my-namespace, DC=svc, DC=cluster, DC=local`
     #[serde(
         rename = "secrets.stackable.tech/backend.autotls.cert.domain-components-in-subject-dn",
         deserialize_with = "SecretVolumeSelector::deserialize_str_as_bool",