update the definition of changed (#71865)

* add nuance to the definition of changed, add notes to modules that return "changed" without changing state

changelogs/fragments/changed_clarified.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - clarified changed status to reflect existing rule that had never been written down.

docs/docsite/rst/reference_appendices/common_return_values.rst

@@ -23,11 +23,11 @@ For those modules that implement `backup=no|yes` when manipulating files, a path
     .. code-block:: console
 
       "backup_file": "./foo.txt.32729.2020-07-30@06:24:19~"
-    
+
 
 changed
 ```````
-A boolean indicating if the task had to make changes.
+A boolean indicating if the task had to make changes to the target or delegated host.
 
     .. code-block:: console
 

lib/ansible/modules/add_host.py

@@ -37,6 +37,7 @@ notes:
 - Since Ansible 2.4, the C(inventory_dir) variable is now set to C(None) instead of the 'global inventory source',
   because you can now have multiple sources.  An example was added that shows how to partially restore the previous behaviour.
 - Windows targets are supported by this module.
+- Though this module does not change the remote host, we do provide 'changed' status as it can be useful for those trying to track inventory changes.
 seealso:
 - module: ansible.builtin.group_by
 author:

lib/ansible/modules/group_by.py

@@ -31,6 +31,7 @@ options:
 notes:
 - Spaces in group names are converted to dashes '-'.
 - This module is also supported for Windows targets.
+- Though this module does not change the remote host, we do provide 'changed' status as it can be useful for those trying to track inventory changes.
 seealso:
 - module: ansible.builtin.add_host
 author: