Get Azure Tenant ID from Name

Get-AzTenantId.ps1

function Get-AzTenantId {
<#
.SYNOPSIS
    Resolves the tenant ID for a specified name.
.OUTPUTS
    System.Guid. The Tenant ID of the specified name
#>
    [CmdletBinding()]
    param(
        #The tenant string you wish to resolve. Examples include: mydomain.com, myorg.onmicrosoft.com
        [Parameter(Mandatory,ValueFromPipeline)][String]$Tenant
    )

    process {
        if ([Uri]::CheckHostName($Tenant) -ne [UriHostNameType]::Dns) {
            Write-Error "$Tenant is not a valid DNS name. Please specify something like mydomain.com or myorg.onmicrosoft.com"
            return
        }
        try {
            $endpoint = (Invoke-RestMethod -UseBasicParsing -ErrorAction Stop -Uri "https://login.microsoftonline.com/$Tenant/v2.0/.well-known/openid-configuration").authorization_endpoint
        } catch [Microsoft.PowerShell.Commands.HttpResponseException] {
            if ($_.FullyQualifiedErrorId -eq 'WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand') {
                [PSCustomObject]$errorResponse = $PSItem.ErrorDetails.Message | ConvertFrom-Json
                Write-Error ("{0}: {1}" -f $errorResponse.error, $errorResponse.error_description)
                return
            } else {
                Write-Error -ErrorRecord $PSItem
                return
            }
        }
        $guidRegex = '(\w{8}-\w{4}-\w{4}-\w{4}-\w{12})'
        if ($endpoint -notmatch $guidRegex) {
            Write-Error "Query succeeded but unable to resolve an Id for $Tenant. This is probably a bug." 
            return
        }
        return [guid]::Parse($matches[1])
    }
}