Action silently fails when there is too much text

[mcasperson]

Attempting to send a large amount of text in a block results in the action silently failing.

I found that when I attempted to recreate the webhook API call in a tool like Postman, I was getting an invalid_blocks response. This appears to be because I ran over the character limit for a block (my post was over 5000 characters), as discussed on StackOverflow.

But the GitHub Action never reported any error and succeeded. I would have expected the failed API call to result in the action also failing.