Example of idempotent (pseudo-)random() usage. (#31048)

Add note to use idempotent random() seed based on inventory_hostname.

docs/docsite/rst/playbooks_filters.rst

@@ -452,6 +452,9 @@ To get a sha256 password hash with a specific salt::
 
     {{ 'secretpassword'|password_hash('sha256', 'mysecretsalt') }}
     
+An idempotent method to generate unique hashes per system is to use a salt that is consistent between runs::
+
+    {{ 'secretpassword'|password_hash('sha512', 65534|random(seed=inventory_hostname)|string) }}
 
 Hash types available depend on the master system running ansible,
 'hash' depends on hashlib password_hash depends on passlib (http://passlib.readthedocs.io/en/stable/lib/passlib.hash.html).