New-AzADUser requires -MailNickname but parameter is not required

[maddieclayton]

Description

New-AzADUser throws when -MailNickname is not provided, but the parameter is not required. Not sure if this parameter should be required or if there is some other issue with the cmdlet code.
PR where this issue was discovered: https://github.com/Azure/azure-powershell/pull/8212/files

Script/Steps for Reproduction

PS C:\svn\obs\azure\scripts> $SecureStringPassword = ConvertTo-SecureString -String "TxQl77FS*#m9" -AsPlainText -Force
New-AzADUser -DisplayName "dnhf01-test01" -UserPrincipalName "dnhf01-test03@xyz.onmicrosoft.com" -Password $SecureStringPassword
New-AzADUser : 'MailNickname' cannot be null.
At line:2 char:1
+ New-AzADUser -DisplayName "dnhf01-test01" -UserPrincipalName "dnhf01- ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : CloseError: (:) [New-AzADUser], ValidationException
    + FullyQualifiedErrorId : Microsoft.Azure.Commands.ActiveDirectory.NewAzureADUserCommand

Module Version

PS C:\svn\obs\azure\scripts> Get-Module Az

ModuleType Version    Name                                ExportedCommands
---------- -------    ----                                ----------------
Script     1.0.1      Az

Environment Data

$PSVersionTable

Debug Output

[cormacpayne]

This has been fixed and will be available in the next release of Az (2019-01-15).