PowerShell function Get-AADToken - works for both UPN and SPN

Get-AADToken.ps1

Function Get-AADToken {
       
  [CmdletBinding()]
  [OutputType([string])]
  PARAM (
    [Parameter(Position=0,Mandatory=$true)]
    [ValidateScript({
          try 
          {
            [System.Guid]::Parse($_) | Out-Null
            $true
          } 
          catch 
          {
            $false
          }
    })]
    [Alias('tID')]
    [String]$TenantID,

    [Parameter(Position=1,Mandatory=$true)][Alias('cred')]
    [pscredential]
    [System.Management.Automation.CredentialAttribute()]
    $Credential,
    
    [Parameter(Position=0,Mandatory=$false)][Alias('type')]
    [ValidateSet('UserPrincipal', 'ServicePrincipal')]
    [String]$AuthenticationType = 'UserPrincipal'
  )
  Try
  {
    $Username       = $Credential.Username
    $Password       = $Credential.Password

    If ($AuthenticationType -ieq 'UserPrincipal')
    {
      # Set well-known client ID for Azure PowerShell
      $clientId = '1950a258-227b-4e31-a9cf-717495945fc2'

      # Set Resource URI to Azure Service Management API
      $resourceAppIdURI = 'https://management.azure.com/'

      # Set Authority to Azure AD Tenant
      $authority = 'https://login.microsoftonline.com/common/' + $TenantID
      Write-Verbose "Authority: $authority"

      $AADcredential = [Microsoft.IdentityModel.Clients.ActiveDirectory.UserCredential]::new($UserName, $Password)
      $authContext = [Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext]::new($authority)
      $authResult = $authContext.AcquireTokenAsync($resourceAppIdURI,$clientId,$AADcredential)
      $Token = $authResult.Result.CreateAuthorizationHeader()
    } else {
      # Set Resource URI to Azure Service Management API
      $resourceAppIdURI = 'https://management.core.windows.net/'

      # Set Authority to Azure AD Tenant
      $authority = 'https://login.windows.net/' + $TenantId

      $ClientCred = [Microsoft.IdentityModel.Clients.ActiveDirectory.ClientCredential]::new($UserName, $Password)
      $authContext = [Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext]::new($authority)
      $authResult = $authContext.AcquireTokenAsync($resourceAppIdURI,$ClientCred)
      $Token = $authResult.Result.CreateAuthorizationHeader()
    }
    
  }
  Catch
  {
    Throw $_
    $ErrorMessage = 'Failed to aquire Azure AD token.'
    Write-Error -Message 'Failed to aquire Azure AD token'
  }
  $Token
}