Added documentation for hostswithgroup() policy function

Ticket: ENT-11325
Signed-off-by: Victor Moene <victor.moene@northern.tech>

Author: victormlg

reference/functions/hostswithclass.markdown

@@ -18,7 +18,7 @@ hostnames, ip-addresses or public key SHAs of hosts that have a given class.
 configuration files for (classes of) hosts. Hosts are selected based on the
 classes set during the most recently collected agent run.
 
-[%CFEngine_function_attributes(class, field, hostkey)%]
+[%CFEngine_function_attributes(class, field)%]
 
 **Example:**
 

reference/functions/hostswithgroup.markdown

@@ -0,0 +1,37 @@
+---
+layout: default
+title: hostswithgroup
+published: true
+---
+
+**This function is only available in CFEngine Enterprise.**
+
+[%CFEngine_function_prototype(group_name, field)%]
+
+**Description:** Returns a list from the CFEngine Database with the information `field` of all hosts sharing the group `group_name`.
+
+On CFEngine Enterprise, this hub function can be used to return a list of hostnames, ip-addresses or public key SHAs of hosts that are from the same group. It works very similarly as its twin `hostswithclass()`.
+
+[%CFEngine_function_attributes(group_name, field)%]
+
+**Example:**
+
+```cf3
+bundle agent debian_hosts
+{
+vars:
+
+  am_policy_hub::
+    "host_list" slist => hostswithgroup( "Linux", "name" );
+
+files:
+  am_policy_hub::
+    "/tmp/master_config.cfg"
+         edit_line => insert_lines("host=$(host_list)"),
+            create => "true";
+}
+```
+
+**History:** Was introduced in 3.26.0
+
+**See also:** `hostswithclass()`