add consumer groups

Author: paulohtb6

modules/deploy/pages/redpanda/manual/resilience/shadowing.adoc

@@ -247,6 +247,30 @@ acl_filters:
       host: "*"                         # Any host
 ----
 
+==== Consumer group filtering and behavior
+
+Consumer group filters determine which consumer groups have their offsets replicated to the shadow cluster. By default, all consumer groups are replicated unless you specify filters.
+
+[,yaml]
+----
+consumer_offset_sync_options:
+  enabled: true
+  interval: "30s"
+  group_filters:
+    - pattern_type: "PREFIX"
+      filter_type: "INCLUDE"
+      name: "prod-consumer-"             # Include production consumer groups
+    - pattern_type: "LITERAL"
+      filter_type: "EXCLUDE"
+      name: "test-consumer-group"        # Exclude specific test groups
+----
+
+**Important consumer group considerations:**
+
+**Avoid name conflicts:** If you plan to consume data from the shadow cluster, do not use the same consumer group names as those used on the source cluster. While this won't break shadow linking, it can impact your RPO/RTO because conflicting group names may interfere with offset replication and consumer resumption during disaster recovery.
+
+**Offset clamping:** When Redpanda replicates consumer group offsets from the source cluster, offsets are automatically "clamped" during the commit process. If a replicated offset is above the high watermark (HWM) of the shadow partition, Redpanda clamps the offset to the shadow partition's HWM. This ensures offsets remain valid and prevents consumers from seeking beyond available data on the shadow cluster.
+
 ==== Schema Registry synchronization
 
 Shadowing can replicate Schema Registry data by shadowing the `_schemas` system topic. When enabled, this provides byte-for-byte replication of schema definitions, versions, and compatibility settings.