Adds details to the password_hash documentation (#82419)

fix for issue 82415

-

Co-authored-by: Alicia Cozine <acozine@users.noreply.github.com>
Co-authored-by: Felix Fontein <felix@fontein.de>

lib/ansible/plugins/filter/password_hash.yml

@@ -7,6 +7,7 @@ DOCUMENTATION:
   positional: _input
   notes:
     - Algorithms available might be restricted by the system.
+    - Algorithms may restrict salt length or content. For example, Blowfish/bcrypt requires a 22-character salt.
   options:
     _input:
       description: Secret to hash.
@@ -18,7 +19,7 @@ DOCUMENTATION:
       default: sha512
       choices: [ md5, blowfish, sha256, sha512 ]
     salt:
-      description: Secret string that is used for the hashing, if none is provided a random one can be generated.
+      description: Secret string used for the hashing. If none is provided a random one can be generated. Use only numbers and letters (characters matching V([./0-9A-Za-z]+)).
       type: string
     rounds:
       description: Number of encryption rounds, default varies by algorithm used.