x-pack/filebeat/docs/ - document gzip S3 object handling (#42306)

Document how compressed objects are handled by the aws-s3 input.

(cherry picked from commit 7fd2d46)

x-pack/filebeat/docs/inputs/input-aws-s3.asciidoc

@@ -172,13 +172,22 @@ Node pipeline.
 }
 ----
 
+[float]
+=== Handling Compressed Objects
+
+S3 objects that use the gzip format
+(https://rfc-editor.org/rfc/rfc1952.html[RFC 1952]) with the DEFLATE compression
+algorithm are automatically decompressed during processing. This is achieved by
+checking for the gzip file magic header.
+
 [float]
 === Configuration
 
 The `aws-s3` input supports the following configuration options plus the
 <<{beatname_lc}-input-{type}-common-options>> described later.
 
-NOTE: For time durations, valid time units are - "ns", "us" (or "µs"), "ms", "s", "m", "h". For example, "2h"
+NOTE: For time durations, valid time units are - "ns", "us" (or "µs"), "ms",
+"s", "m", "h". For example, "2h"
 
 [float]
 ==== `api_timeout`