Propagate input id from the Agent policy into Filebeat configuration (#…

…30386)

* Propage input id from the Agent policy into Filebeat configuration

This allow an ID defined on the Agent Policy for any inputs supported by
Filebeat to be propaged down to the Filebeat configuration.

Note: No validation is done on the field, if the field is present it will sent to
Filebeat.

Fixes: #30300

x-pack/elastic-agent/CHANGELOG.next.asciidoc

@@ -163,3 +163,4 @@
 - Add support for loading input configuration from external configuration files in standalone mode. You can load inputs from YAML configuration files under the folder `{path.config}/inputs.d`. {pull}30087[30087]
 - Install command will skip install/uninstall steps when installation via package is detected on Linux distros. {pull}30289[30289]
 - Add support for enabling the metrics buffer endpoint in the elastic-agent and beats it runs. diagnostics collect command will gather metrics-buffer data if enabled. {pull}30471[30471]
+- Elastic Agent now propagates ID for Filebeat input. {pull}30386[30386]

x-pack/elastic-agent/pkg/agent/program/testdata/usecases/generated/single_config.filebeat.golden.yml

@@ -1,6 +1,7 @@
 filebeat:
   inputs:
-  - index: logs-generic-default
+  - id: logfile-1
+    index: logs-generic-default
     paths:
     - /var/log/hello1.log
     - /var/log/hello2.log
@@ -28,7 +29,8 @@ filebeat:
     type: log
     vars:
       var: value
-  - index: testtype-generic-default
+  - id: logfile-2
+    index: testtype-generic-default
     paths:
     - /var/log/hello3.log
     - /var/log/hello4.log

x-pack/elastic-agent/pkg/agent/program/testdata/usecases/single_config.yml

@@ -53,6 +53,7 @@ inputs:
         dataset: ""
   hosts: ["http://127.0.0.1:8080"]
 - type: logfile
+  id: logfile-1
   use_output: default
   streams:
     - paths:
@@ -61,6 +62,7 @@ inputs:
   vars:
     var: value
 - type: logfile
+  id: logfile-2
   data_stream:
     type: testtype
   use_output: default

x-pack/elastic-agent/spec/filebeat.yml

@@ -24,7 +24,7 @@ rules:
     - copy_all_to_list:
         to: streams
         on_conflict: noop
-        except: ["streams", "id", "enabled", "processors"]
+        except: ["streams", "enabled", "processors"]
     - copy_to_list:
         item: processors
         to: streams