Powershell script to get a token for my app environment

get-token.ps1

<#
.SYNOPSIS
    Get access token for a specified <app> environment
.DESCRIPTION
    Fetches required secrets from Azure key vault, and used azure CLI to get a token.
.PARAMETER environment
    Which <app> environment to authenticate against (eg. dev, test, prod)
    Default: dev
#>
param (
    [Alias("e")]
    [string]$environment = "dev",
    [Alias("s")]
    [switch]$silent,
    [Alias("c")]
    [switch]$clipboard
)

[string] $environments = "dev", "test", "prod"

$banner = @"
   __      _   _                 _             _        _                _ 
  / /  ___| |_( )__    __ _  ___| |_    __ _  | |_ ___ | | _____ _ __   / \
 / /  / _ \ __|/ __|  / _`` |/ _ \ __|  / _`` | | __/ _ \| |/ / _ \ '_ \ /  /
/ /__|  __/ |_ \__ \ | (_| |  __/ |_  | (_| | | || (_) |   <  __/ | | /\_/ 
\____/\___|\__||___/  \__, |\___|\__|  \__,_|  \__\___/|_|\_\___|_| |_\/   
                      |___/                                                
"@

if (!$silent) {
    Write-Host -ForegroundColor White $banner
    Write-Host ""
}

try {
    $userName = (az account show --query "user.name" --output tsv)
    if ($null -eq $username || -not $?) {
        Write-Host 
        Write-Host -ForegroundColor White "Not logged in? Run 'az login' first."
        Exit 1
    }

    if (!$environments.contains($environment)) {
        Write-Host -ForegroundColor White "$environment is not a valid environment."
        Exit 1
    }

    $environmentKeyvault = "<app>-{env}-kv".Replace("{env}", $environment)
    if (!$silent) {
        Write-Host "Logged in as $userName."
        Write-Host "Using key vault $environmentKeyVault for <app> $environment."
        Write-Host ""
    }

    $scope = (az keyvault secret show --vault-name $environmentKeyvault --name "AzureAd--Resource" --query "value" --output tsv)

    if ([string]::IsNullOrEmpty($scope)) {
        Write-Host -ForegroundColor White "Unable to get scope from keyvault."
        Exit 1
    }

    $token = (az account get-access-token --scope $scope --query accessToken --output tsv)
    if ([string]::IsNullOrEmpty($token)) {
        Write-Host -ForegroundColor White "Did not get a token, not sure why :|"
        Exit 1
    }
    if ($silent -eq $false) {
        Write-Host "Retrieved token for <app> $environment, scope $scope"
        Write-Host
    }
    if ($clipboard) {
        Set-Clipboard -Value $token
        if (!$silent) {
            Write-Host "Token copied to clipboard."
        }
    }
    else {
        Write-Output $token
    }
    Exit 0
}
catch {
    $errorMessage = ConvertFrom-Json $_.ErrorDetails.Message
    Write-Host
    Write-Host $errorMessage.error
    Write-Host $errorMessage.error_description
    Exit 1
}

if ($silent -eq $false) {
    Write-Host "Done!"
}