Slack posting by webhooks implementation of links isn't working

[instantiator]

Context

When posting by Webhook, we can see that links aren't being rendered.

Hypothesis

This could be caused by a malformed or not fully formed block created in SlackWebhookConnection

case SnippetType.Link:
  text.RequireText("Text");
  reference.RequireText("Link");
  blocks.Add(new SlackWebhookPostBlock()
  {
      text = new SlackWebhookPostBlockText()
      {
          text = $"<{reference!}|{text!}>",
          type = "mrkdwn"
      },
  });
  break;

It might be better to render this as a rich text section inside a rich text block.

Block-kit looks like a powerful tool that we are not yet using to its full potential.

We can use the block-kit builder to experiment with the right combination of block types.

[instantiator]

Working branch: P36_improved-typing-for-BlockKit