1. There seems to be no documentation about how to verify requests using the Java SDK. The only documentation found is the general info.
2. When trying to verify a Slack incoming request, we need to pass in the full URL-encoded body. However, the Java standard library does not URL-encode the aterix character *, thus resulting in an automatic failure if present in the payload. A notice or warning about how to correctly handle that would save some time.

The page URLs

No pages - to add in a new example or page.

Requirements

1. Indicate that the app_backend module contains a helper to validate incoming Slack requests
2. For Spring use, indicate that receiving a ContentCachingRequestWrapper allows for reading a raw request body, else it will be automatically deserialized.
3. When calling the SlackSignature.Verifier method, indicate that the payload must be url-encoded, including for asterix, and that there may be a need to encode the * character manually (to %2A).