Public/Add-MITGroupMember.ps1

function Add-MITGroupMember{
    <#
    .SYNOPSIS
        Add MOVEit Transfer Group Member(s)
    .LINK
        Add members(s) to group
        https://docs.ipswitch.com/MOVEit/Transfer2021/Api/Rest/#operation/POSTapi/v1/groups/{Id}/members-1.0
    #>

    [CmdletBinding()]
    param (
        [Parameter(Mandatory,
                    Position=0,
                    ValueFromPipelineByPropertyName=$true)]
        [Alias('Id')]                    
        [string]$GroupId,

        [Parameter(Mandatory)]
        [string[]]$UserIds
    )
    
    try {
        # Confirm the token, refreshing if necessary
        Confirm-MITToken

        # Set the Uri for this request
        $uri = "$script:BaseUri/groups/$GroupId/members"
                    
        # Set the request headers
        $headers = @{
            Accept = "application/json"
            Authorization = "Bearer $($script:Token.AccessToken)"        
        }

        # Build the request body.
        $body = @{}
        switch ($PSBoundParameters.Keys) {
            GroupId { $body['id'] = $GroupId }
            UserIds { $body['userIds'] = $UserIds }
        }

        # Setup the params to splat to IRM
        $irmParams = @{
            Uri = $uri
            Method = 'Post'
            Headers = $headers
            ContentType = 'application/json'
            Body = ($body | ConvertTo-Json)
        }

        # Send the request and output the response
        $response = Invoke-RestMethod @irmParams
        $response | Write-MITResponse -TypeName 'MITUserSimple'
    }
    catch {
        $PSCmdlet.ThrowTerminatingError($PSItem)
    }
}