developer/api/v1/apps/Update-ApplicationCertificate.ps1

function Update-ApplicationCertificate
{
    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter(Mandatory)]
        [string] $AppAlias,
        [Parameter(Mandatory)]
        [string] $FilePath
    )

    if ($PSCmdlet.ShouldProcess($AppAlias))
    {
        return Invoke-Api Put "/developer/api/v1/apps/$AppAlias/customUrlCertificate" -FileBody $FilePath
    }
}