Fetch an accesstoken from IdentityServer3 using PowerShell 3

GetToken.ps1

<#
.SYNOPSIS
    Fetches an access token using the IdentityServer3 token endpoint 
.DESCRIPTION
    Modify the parameters so it matches your IdentityServer3 instance.
.NOTES
    File Name      : GetToken.ps1
    Author         : John Korsnes (@johnkors, johnkors)
    Prerequisite   : PowerShell V3    
.LINK    
    https://identityserver.github.io/Documentation/docsv2/endpoints/token.html
#>

$identityserverUrl = "https://localhost:44333/core"
$tokenendpointurl = $identityserverUrl + "/connect/token"
$granttype = "client_credentials" # client_credentials / password 
$client_id = ""
$client_secret = ""
$username = ""
$password = ""
$scope = ""

function Convert-FromBase64StringWithNoPadding([string]$data)
{
    $data = $data.Replace('-', '+').Replace('_', '/')
    switch ($data.Length % 4)
    {
        0 { break }
        2 { $data += '==' }
        3 { $data += '=' }
        default { throw New-Object ArgumentException('data') }
    }
    return [System.Convert]::FromBase64String($data)
}

function FetchToken
{
    $body = @{
        grant_type = $granttype
        scope = $scope
        client_id = $client_id
        client_secret = $client_secret    
        username = $username
        password = $password
    }
        
    $resp = Invoke-RestMethod -Method Post -Body $body -Uri $tokenendpointurl 
    $parts = $resp.access_token.Split('.');

    $baseDecoded = Convert-FromBase64StringWithNoPadding($parts[1])
    $decoded = [System.Text.Encoding]::UTF8.GetString($baseDecoded)

    Write-Host "`***** SUCCESSFULLY FETCHED TOKEN ***** `n" -foreground Green

    Write-Host "`JWT payload: `n" -foreground Yellow
    $decoded = $decoded | ConvertFrom-Json | ConvertTo-Json
    Write-Host $decoded -foreground White

    Write-Host
    Write-Host "`ACCESSTOKEN: `n" -foreground Yellow
    Write-Host ($resp.access_token | Format-Table -Wrap | Out-String ) -foreground White
    Write-Host    
}  

cls
try
{
    FetchToken
}
catch 
{          
     Write-Host "`***** FETCHING TOKEN EXPERIENCED ERROR ***** `n" -foreground Red     
     Write-Host $_  -foreground Red
     Write-Host     
}