* Ensure we work on only one user.
After the initial get/create use the GUID of the found/created user to
ensure we will not start to work with a different user. If we create a
user or modify it's attributes an he is not identified with the name
parameter afterwards this module fails in rather unpredictable ways.
This addressed #45298
* Use splatting create_args for creating user.
This prepars this for adding more optional create arguments without
nesting of condictions.
* Set the UserPrincipalName and SamAccountName on create.
Set the UserPrincipalName and SamAccountName on the create operation if
upn is given to ensure the User is created with a contollable
SamAccountName.
* Rename $username to $name.
$username is missleading as its not the SamAccountName.
* Add a identity parameter to win_domain_user
This gives the user full controll over how the user is identified in the
AD.
* Add version_added information for new parameter and fix yaml syntax.
* Added changelog fragment
