[DOCS] Adds information about compatibility mode in Connecting

Author: picandocodigo

docs/connecting.asciidoc

@@ -9,6 +9,7 @@ This page contains the information you need to connect and use the Client with
 * <<client-auth, Authentication options>>
 * <<client-usage, Using the client>>
 * <<client-faas, Using the Client in a Function-as-a-Service Environment>>
+* <<client-comp, Enabling the Compatibility Mode>>
 
 [discrete]
 [[client-auth]]
@@ -219,3 +220,11 @@ Resources used to assess these recommendations:
 
 * https://cloud.google.com/functions/docs/bestpractices/tips#use_global_variables_to_reuse_objects_in_future_invocations[GCP Cloud Functions: Tips & Tricks]
 * https://docs.aws.amazon.com/lambda/latest/dg/best-practices.html[Best practices for working with AWS Lambda functions]
+
+[discrete]
+[[client-comp]]
+=== Enabling the Compatibility Mode
+
+The Elasticsearch server version 8.0 is introducing a new compatibility mode that allows you a smoother upgrade experience from 7 to 8. In a nutshell, you can use the latest 7.x Elasticsearch client with an 8.x Elasticsearch server, giving more room to coordinate the upgrade of your codebase to the next major version.
+
+If you want to leverage this functionality, please make sure that you are using the latest 7.x client and set the environment variable `ELASTIC_CLIENT_APIVERSIONING` to `true`. The client is handling the rest internally. For every 8.0 and beyond client, you're all set! The compatibility mode is enabled by default.