Fixes #37654 - Use custom snippets to apply errata

Refs 2064ec7457b3d41b72c2d48b7df9371f8b09d053 in katello

Closes #3157

guides/common/assembly_managing-errata.adoc

@@ -8,6 +8,8 @@ include::modules/ref_parameters-available-for-errata-search.adoc[leveloffset=+1]
 
 include::modules/proc_applying-installable-errata.adoc[leveloffset=+1]
 
+include::modules/proc_running-custom-code-while-applying-errata.adoc[leveloffset=+1]
+
 include::modules/con_subscribing-to-errata-notifications.adoc[leveloffset=+1]
 
 :package-manager: dnf

guides/common/modules/proc_running-custom-code-while-applying-errata.adoc

@@ -0,0 +1,37 @@
+[id="running-custom-code-while-applying-errata_{context}"]
+= Running custom code while applying errata
+
+You can use custom snippets to run code before and/or after applying errata on hosts.
+
+.Prerequisites
+* Check your provisioning template to ensure that it supports the custom snippets you want to use.
++
+You can view all job templates that are in use under *Administer* > *Remote Execution Features*.
+
+.Procedure
+. In the {ProjectWebUI}, navigate to *Hosts* > *Templates* > *Job Templates*.
+. Click *Create Template*.
+. In the *Name* field, enter a name for your custom snippet.
+The name must start with the name of a template that supports custom snippets:
+** Append `custom pre` to the name of a template to run code before applying errata on hosts.
+** Append `custom post` to the name of a template to run code after applying errata on hosts.
+
++
+If your template is called `Install Errata - Katello Ansible Default`, name your template `Install Errata - Katello Ansible Default custom pre` or `Install Errata - Katello Ansible Default custom post`.
+. On the *Type* tab, select *Snippet*.
+. Click *Submit* to create your custom snippet.
+
+[id="cli-running-custom-code-while-applying-errata_{context}"]
+.CLI procedure
+. Create a plain text file that contains your custom snippet.
+. Create the template using `hammer`:
++
+[options="nowrap" subs="+quotes"]
+----
+# hammer template create \
+--file "~/_My_Snippet_" \
+--locations "_My_Location_" \
+--name "_My_Template_Name_custom_pre" \
+--organizations "_My_Organization_" \
+--type snippet
+----