Document SSL reloading with Let's Encrypt

See gh-50222

Signed-off-by: henriquejsza <henriquejsza@gmail.com>

spring-boot-project/spring-boot-docs/src/docs/antora/modules/reference/pages/features/ssl.adoc

@@ -181,3 +181,31 @@ A file watcher is then watching the files and if they change, the SSL bundle wil
 This in turn triggers a reload in the consuming component, e.g. Tomcat rotates the certificates in the SSL enabled connectors.
 
 You can configure the quiet period (to make sure that there are no more changes) of the file watcher with the configprop:spring.ssl.bundle.watch.file.quiet-period[] property.
+
+[[features.ssl.reloading.lets-encrypt]]
+=== Reloading SSL Bundles With Let's Encrypt
+
+If you use certificates issued by https://letsencrypt.org/[Let's Encrypt] and renewed by an external tool, such as https://certbot.eff.org/[Certbot], you can configure a PEM bundle to use the files from the `live` directory and enable reloading:
+
+[configprops,yaml]
+----
+    spring:
+      ssl:
+        bundle:
+          pem:
+            web-server:
+              reload-on-update: true
+              keystore:
+                certificate: "file:/etc/letsencrypt/live/example.com/fullchain.pem"
+                private-key: "file:/etc/letsencrypt/live/example.com/privkey.pem"
+    server:
+      ssl:
+        bundle: "web-server"
+----
+
+Spring Boot does not request or renew Let's Encrypt certificates.
+When Certbot or another ACME client updates the configured files, the SSL bundle is reloaded.
+Compatible consumers, such as Tomcat and Netty web servers, can then use the updated certificate without restarting the application.
+
+The files in `/etc/letsencrypt/live` are typically symbolic links to files in `/etc/letsencrypt/archive`.
+The file watcher follows symbolic links so that updates to the target files can trigger a reload.