Update data streams documentation to note that sprintf syntax is unsupported

CHANGELOG.md

@@ -1,3 +1,6 @@
+## 12.1.1
+ - Update documentation to state that that sprintf syntax is not supported for datastreams, and give a workaround [#1224](https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/1224)
+
 ## 12.1.0
  - Add drop_error_types config option to not retry after certain error types [#1228](https://github.com/logstash-plugins/logstash-output-elasticsearch/pull/1228)
 

docs/index.asciidoc

@@ -136,6 +136,22 @@ output {
 }
 -----
 
+NOTE: Dynamic variable substitution using sprintf syntax, such as %{foo}, is not supported in the `data_stream` options
+      at this time. If you want to dynamically route to data streams, you can add the appropriate fields to events in
+      the configuration and take advantage of the (on by default) auto routing facility:
+
+[source,sh]
+-----
+filter {
+      mutate {
+              add_field => {
+                      "[data_stream][type]" => "logs"
+                      "[data_stream][dataset]" => "%{dataset_name}"
+                      "[data_stream][namespace]" => "%{namespace_name}"
+              }
+      }
+}
+-----
 
 ==== Writing to different indices: best practices
 

logstash-output-elasticsearch.gemspec

@@ -1,6 +1,6 @@
 Gem::Specification.new do |s|
   s.name            = 'logstash-output-elasticsearch'
-  s.version         = '12.1.0'
+  s.version         = '12.1.1'
   s.licenses        = ['apache-2.0']
   s.summary         = "Stores logs in Elasticsearch"
   s.description     = "This gem is a Logstash plugin required to be installed on top of the Logstash core pipeline using $LS_HOME/bin/logstash-plugin install gemname. This gem is not a stand-alone program"