Basic Microsoft Graph Authentication in Powershell

MicrosoftGraphAuth.ps1

[CmdletBinding()]
param (
    [Parameter(Mandatory=$True)]
    [string]
    $TenantName,

    [Parameter(Mandatory=$True)]
    [string]
    $AppId,

    [Parameter(Mandatory=$True)]
    [string]
    $AppSecret
)

begin {
    $Scope = 'https://graph.microsoft.com/.default'
    $TokenUrl = "https://login.microsoftonline.com/$($TenantName)/oauth2/v2.0/token"
    
    $Body = @{
        client_id = $AppId
        client_secret = $AppSecret
        scope = $Scope
        grant_type = 'client_credentials'
    }
    
    $PostSplat = @{
        ContentType = 'application/x-www-form-urlencoded'
        Method = 'POST'
        Body = $Body
        Uri = $TokenUrl
    }
    
    try {
        $Request = Invoke-RestMethod @PostSplat
    }
    catch {
        throw $_
    }

    $Headers = @{
        Authorization = "{0} {1}" -f ($Request.token_type, $Request.access_token)
    }
}

process {
    $Me = Invoke-RestMethod -Uri "https://graph.microsoft.com/v1.0/me" -Method GET -Headers $Headers
    $Me
}

end {
    
}