Add RemoveDefault() extension method to fluent API for CMS webhook events

[ronaldbarendse]

Prerequisites

• I have added steps to test this contribution in the description below

Description

PR #15345 added a fluent API for adding webhook events, but because the CMS adds a subset of events by default, you had to first clear all events to make sure you only end up with the configured ones. However, if other packages (like Deploy) also add events by default, those will also be cleared.

To address this, I've added a RemoveDefault() extension method, so the following example ensures all CMS default events are removed and only the content ones are added, without affecting other custom/non-CMS events:

using Umbraco.Cms.Core.Composing;

public class WebhookComposer : IComposer
{
    public void Compose(IUmbracoBuilder builder)
        => builder.WebhookEvents()
            .AddCms(cmsBuilder => cmsBuilder.RemoveDefault().AddContent());
}

[ronaldbarendse]

A quick update on this: we've implemented the RemoveDefault() extension method on both Deploy and Forms, so would be nice to have the CMS align on this as well!

[AndyButland]

Looks fine to me and agree it would be nice to have this common method across the products.