docs: add 'inserting hosts' section in docs

docs/filters.rst

@@ -22,6 +22,9 @@ Event Filters
      - Include and exclude keys from the event object
    * - dashes_to_underscores
      - This filter changes the dashes in all keys in the payload to be underscore.
+   * - insert_hosts_to_meta
+     - This filter inserts the hosts from the event into the meta key within the event
+       based on a custom path in the event object.
 
 | Events filters can be chained one after the other, and the updated data is
 | sent from one filter to the next.
@@ -30,7 +33,7 @@ Event Filters
 | When the rulebook starts the Source plugin it associates the correct filters
 | and transforms the data before putting it into the queue.
 
-e.g.
+Examples:
 
 .. code-block:: yaml
 

docs/host_limit.rst

@@ -17,3 +17,31 @@ Event data example:
 The value for "hosts" can be a comma delimited string of multiple host names, but typically
 it is a single host. This is useful to restrict a remedy playbook to run only on the problematical host
 that emits a monitored event. Be sure that the source plugin already sends this metadata.
+
+
+Inserting hosts to meta
+-----------------------
+
+The plugins may not send metadata like for example the `ansible.eda.webhook` plugin which
+sends the arbitrary payload under the `payload` key.
+
+To accommodate this, the EDA collection provides the `insert_hosts_to_meta` filter,
+allowing any plugin to customize the value of `event.meta.hosts` based on the contents
+of a specific key in the event.
+
+.. note::
+
+    The host_path argument in the filter `insert_hosts_to_meta` does not need the `event.` prefix
+    like conditions or action arguments.
+
+
+Example:
+
+.. code-block:: yaml
+
+    sources:
+        - ansible.eda.webhook:
+            port: 4444
+          filters:
+            - ansible.eda.insert_hosts_to_meta:
+                host_path: "payload.alert.instances"