Fetches a cached bearer token for Helpscout authentication 2.0, refreshing it if necessary

Get-HelpscoutToken.ps1

Function Get-HelpscoutToken
{
#Fetches a cached bearer token for Helpscout authentication 2.0, refreshing it if necessary
#returns the token as plaintext for easy integration into invoke-restmethod

    [CmdletBinding()]
    Param(
        [Parameter(Mandatory=$True)]
        [string]$helpscout_token_path,

        [Parameter(Mandatory=$true)]
        [securestring]$app_id,

        [Parameter(Mandatory=$true)]
        [securestring]$app_secret,

        [Parameter(Mandatory=$false)]
        [switch]$Force
    )

    $token_request = "https://api.helpscout.net/v2/oauth2/token?grant_type=client_credentials&client_id=$(Get-PlainText $app_id)&client_secret=$(Get-PlainText $app_secret)"

    if (!(Test-Path $helpscout_token_path)){
        Write-Debug "Acquiring helpscout authorization token"
        $response1 = Invoke-RestMethod -Method Post -Uri $token_request -ContentType "application/json; charset=UTF-8"
        $token = ConvertTo-SecureString -String $($response1.access_token) -AsPlainText -Force
        $secureStringText = $token | ConvertFrom-SecureString
        #save the token to disk
        New-Item -Path $helpscout_token_path -ItemType "file" -Value $secureStringText -Force | Out-Null
    }else{
        $token = Get-Content $helpscout_token_path | ConvertTo-SecureString
        $timestamp = Get-Item -Path $helpscout_token_path | Select-Object -ExpandProperty LastWriteTime
        #check to see if the timestamp on the file is more than 2 hours old
        if(((get-date) -gt ($timestamp.AddSeconds(7200))) -or $force){
            #if it is then acquire a new token
            $response2 = Invoke-RestMethod -Method Post -Uri $token_request -ContentType "application/json; charset=UTF-8"
            $token = ConvertTo-SecureString -String $($response2.access_token) -AsPlainText -Force
            $secureStringText = $token | ConvertFrom-SecureString
            #update the token to disk
            Set-Content -Path $helpscout_token_path -Value $secureStringText -Force
        }
    }

    return (Get-PlainText -SecureString $token)
}