xService: Rename BuiltinAccount, Credential and GroupManagedServiceAccount parameters

[danielboth]

Details of the scenario you tried and the problem that is occurring

Currently, the user account used to run the service is returned in the BuiltinAccount property, even if it's setup using the Credential or GroupManagedServiceAccount property. This is inconsistent behavior, as a resource should always return all properties in Get-TargetResource. This issue is the result of a discussion in #441.

Verbose logs showing the problem

N/A

Suggested solution to the issue

Rename the parameters BuiltinAccount, Credential and GroupManagedServiceAccount. For example, we could go with:

• UserName: The user to run the service
• UserType: The type of the user in UserName, for example Builtin, GroupManaged or Password
• Credential: Optional parameter with the credential of the user, this is still needed because the .mof schema of the script based resources does not support securestring. So we need to pass in a credential if we want to supply a password in a somewhat secure manner.

The operating system the target node is running

Applies to both 2012 R2 and 2016+

Version and build of PowerShell the target node is running

5.1

Version of the DSC module that was used ('dev' if using current dev branch)

dev