Bulk Remove JIRA OnDemand Users

$usernamesFile = '.\usernames.csv'
$base = 'https://YOURDOMAIN.jira.com/rest/api/2'

function ConvertTo-Base64($string)
{
    $bytes=[System.Text.Encoding]::UTF8.GetBytes($string);
    $encoded=[System.Convert]::ToBase64String($bytes);
    return $encoded;
}

function Get-HttpBasicHeader
{
    Param([Parameter(Mandatory=$false,
                    ValueFromPipeline=$true,
                    ValueFromPipelineByPropertyName=$true)]
           $credentials=@{}

    )
    $headers=@{}
    if(!$credentials.username)
    {
        $credentials.username=Read-Host 'Input Username'
    }

    if(!$credentials.password)
    {
        $credentials.password=Read-Host 'Input Password'
    }

    $b64=ConvertTo-Base64 ($credentials.username+':'+$credentials.password)
    $headers["Authorization"]='Basic ' + $b64
    return $headers
}

function Get-User
{
    Param( [Parameter(Mandatory=$true)]$header, [Parameter(Mandatory=$true)]$username)
    Invoke-RestMethod -URI ($base+"/user?username="+$username+"&expand=groups") -Headers $header -ContentType 'application/json' -Method Get -Verbose
}

function Remove-UserFromGroup
{
    [CmdletBinding()]
    Param
    (
        [Parameter(Mandatory=$true)]
        $Header,
        $User,
        $Group
    )
    Invoke-RestMethod -URI ($base+"/group/user?groupname="+$Group+"&username="+$User) -Headers $Header -ContentType 'application/json' -Method Delete
}

$usernames = (Get-Content $usernamesFile).Split(",")
$header = Get-HttpBasicHeader

Foreach($user in $usernames)
{
    $userinfo = Get-User $header $user
    Foreach($group in $userinfo.groups.items)
    {
        $group=$group.name.trim()
        $user=$user.trim()
        Remove-UserFromGroup $header $user $group -Verbose
    }
}