This pull request improves the default warning message for unhandled requests by printing suggested code snippets as below:

$ python examples/socket_mode.py
⚡️ Bolt app is running!

Unhandled request ({'token': 'xxx', 'team_id': 'T111', 'api_app_id': 'A111', 'event': {'client_msg_id': 'xxx', 'type': 'message', 'text': 'Hi there!', 'user': 'U222', 'ts': '1620202537.001600', 'team': 'T111', 'channel': 'C111', 'event_ts': '1620202537.001600', 'channel_type': 'channel'}, 'type': 'event_callback', 'event_id': 'Ev111', 'event_time': 1620202537, 'authorizations': [{'enterprise_id': None, 'team_id': 'T111', 'user_id': 'U222', 'is_bot': True, 'is_enterprise_install': False}], 'is_ext_shared_channel': False, 'event_context': '1-message-T111-C111'})
---
[Suggestion] You can handle this type of event with the following listener function:

@app.event("message")
def handle_message_events(body, logger):
    logger.info(body)

With this suggestion, developers, particularly the ones new to bolt-python, can easily understand what to do for handling the requests in their app. This pull request covers all the possible patterns with corresponding code snippets. Refer to the added unit test code (tests/slack_bolt/logger/test_unmatched_suggestions.py) to learn the actual suggestion messages.

If a developer does not want to have the message, we would recommend having raise_error_for_unhandled_request=True in the App/AsyncApp constructor arguments and having their own global error handler (see "Customize Unhandled Error Handling" in the v1.5.0 release notes for more details).

Category (place an x in each of the [ ])

• slack_bolt.App and/or its core components
• slack_bolt.async_app.AsyncApp and/or its core components
• Adapters in slack_bolt.adapter
• Document pages under /docs
• Others

Requirements (place an x in each [ ])

Please read the Contributing guidelines and Code of Conduct before creating this issue or pull request. By submitting, you are agreeing to those rules.

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.
• I've run ./scripts/install_all_and_run_tests.sh after making the changes.