public/Add-TNGroupUser.ps1

function Add-TNGroupUser {
    <#
    .SYNOPSIS
        Adds a list of group users
 
    .DESCRIPTION
        Adds a list of group users
 
    .PARAMETER SessionObject
        Optional parameter to force using specific SessionObjects. By default, each command will connect to all connected servers that have been connected to using Connect-TNServer
 
    .PARAMETER Group
        The target group name. You must specify either Group or GroupId.
 
    .PARAMETER Username
        The target username. You must specify either Username or UserId
 
    .PARAMETER GroupId
        The ID of the target group. You must specify either Group or GroupId.
 
    .PARAMETER UserId
        The ID of the target user. You must specify either Username or UserId.
 
    .PARAMETER EnableException
        By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
        This avoids overwhelming you with 'sea of red' exceptions, but is inconvenient because it basically disables advanced scripting.
        Using this switch turns this 'nice by default' feature off and enables you to catch exceptions with your own try/catch.
 
    .EXAMPLE
        PS C:\> Add-TNGroupUser -Group "Blue Team" -User pbuffet
 
        Adds the pbuffet account to the Blue Team group
 
    .EXAMPLE
        PS C:\> Add-TNGroupUser -GroupId 42 -UserId 10
 
        Adds the user with ID 10 to the group with ID 42, if that's how you want to do it ¯\_(ツ)_/¯
#>

    [CmdletBinding()]
    param
    (
        [Parameter(ValueFromPipelineByPropertyName)]
        [object[]]$SessionObject = (Get-TNSession),
        [Parameter(ValueFromPipelineByPropertyName)]
        [string]$Group,
        [Parameter(ValueFromPipelineByPropertyName)]
        [string[]]$Username,
        [Parameter(ValueFromPipelineByPropertyName)]
        [Int32]$GroupId,
        [Parameter(ValueFromPipelineByPropertyName)]
        [Int32[]]$UserId,
        [switch]$EnableException
    )
    begin {
        if (-not $PSBoundParameters.Group -and -not $PSBoundParameters.GroupId) {
            Stop-PSFFunction -Message "You must specify either Group or GroupId"
            return
        }
        if (-not $PSBoundParameters.Username -and -not $PSBoundParameters.UserId) {
            Stop-PSFFunction -Message "You must specify either Username or UserId"
            return
        }
    }
    process {
        if (Test-PSFFunctionInterrupt) { return }

        foreach ($session in $SessionObject) {
            $PSDefaultParameterValues["*:SessionObject"] = $session
            if ($session.sc) {
                Stop-PSFFunction -Message "tenable.sc not supported" -Continue
            }
            if ($Group) {
                $GroupId = Invoke-TNRequest -SessionObject $session -EnableException:$EnableException -Path '/groups' -Method GET | ConvertFrom-TNRestResponse |
                    Where-Object name -in $Group | Select-Object -ExpandProperty Id
            }
            if ($Username) {
                $UserId += Invoke-TNRequest -SessionObject $session -EnableException:$EnableException -Path '/users' -Method GET | ConvertFrom-TNRestResponse |
                    Where-Object username -in $Username | Select-Object -ExpandProperty Id
            }
            if ($session.MultiUser) {
                foreach ($id in $UserId) {
                    $params = @{
                        SessionObject   = $session
                        Path            = "/groups/$GroupId/users"
                        Method          = 'POST'
                        Parameter       = @{ 'user_id' = $id }
                        EnableException = $EnableException
                    }
                    Invoke-TNRequest @params
                }
            } else {
                Stop-PSFFunction -EnableException:$EnableException -Message "Server ($($session.ComputerName)) for session $($session.sessionid) is not licenced for multiple users" -Continue
            }
        }
    }
}