IDocumentAddedHandler

public interface IDocumentAddedHandler
{
	/// <summary>
	/// Is executed *before* a document is added
	/// </summary>
	/// <param name="document">The document which is going to be added</param>
	Task OnAddingAsync(Document document);

	/// <summary>
	/// Is executed *after* a document has been added
	/// </summary>
	/// <param name="document">The document which was just added</param>
	Task OnAddedAsync(Document document);
}

[DisplayName("Post to Microsoft Teams")]
[Description("Posts added documents to a specified MS Teams channel")]
public class PostToTeamsChannel : IDocumentHandler, IDocumentAddedHandler
{
	[EditorBrowsable]
	[DisplayName("Webhook URL")]
	[Description("Configure the Incoming Webhook connector for the channel you wish to post to.  Paste the webhook URL here.")]
	public string WebhookUrl { get; set; }

	[EditorBrowsable]
	[DisplayName("Message body")]
	[Description("Specify the body of the message.  Use the databinding syntax ({fieldname}) to extract data from the document.")]
	[Editor(PropertyEditors.TextEditor, "")]
	public string MessageBody { get; set; }

	public async Task OnAddedAsync(Document document)
	{
		if (!string.IsNullOrEmpty(WebhookUrl))
		{
			DataBindingContext context = new DataBindingContext(System.Globalization.CultureInfo.CurrentCulture);
			context.AddItem("_Created", document.Created);
			context.AddItem("_DisplayFrom", document.DisplayFrom);
			context.AddItem("_DisplayTo", document.DisplayTo);
			context.AddItem("_Tags", document.TagList);
			context.AddItem("_OwnerId", document.OwnerId);
			context.AddItem("_OwnerName", document.OwnerName);
			context.AddItem("DocumentId", document.Id);
			context.AddItem("UId", document.UID);
			context.AddItem("_OrderIndex", document.OrderIndex);
			context.AddItems(document.FieldValues);

			var messageBody = context.FormatString(MessageBody);

			using (var httpClient = new HttpClient())
			{
				using (var request = new HttpRequestMessage(new HttpMethod("POST"), WebhookUrl))
				{
					request.Content = new StringContent(JsonConvert.SerializeObject(new { text = messageBody }));
					request.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json");
					var response = await httpClient.SendAsync(request);
				}
			}
		}
	}

	public async Task OnAddingAsync(Document document)
	{			
	}
}

public void ConfigureServices(IServiceCollection services, IConfiguration configuration)
{
	services.AddNamed<IDocumentHandler, PostToTeamsChannel>(ServiceLifetime.Transient);
}