Add Agents & Assistants support

[seratch]

This pull request adds the newly added assistant feature to bolt-python. Our teram is still working on the design, so some of the details may be adjusted before merging. This PR relies on https://github.com/slackapi/python-slack-sdk/releases/tag/v3.33.1

assistant = Assistant()
# You can use your own thread_context_store if you want
# from slack_bolt import FileAssistantThreadContextStore
# assistant = Assistant(thread_context_store=FileAssistantThreadContextStore())

@assistant.thread_started
def start_thread(say: Say, set_suggested_prompts: SetSuggestedPrompts):
    say(":wave: Hi, how can I help you today?")
    set_suggested_prompts(
        prompts=[
            "What does SLACK stand for?",
            "When Slack was released?",
        ],
    )

@assistant.user_message
def answer_inquiries(
    payload: dict,
    logger: logging.Logger,
    set_title: SetTitle,
    set_status: SetStatus,
    say: Say,
    get_thread_context: GetThreadContext,
):
    try:
        set_title(payload["text"])
        set_status("Typing...")
        time.sleep(0.3)
        set_status("Still typing...")
        time.sleep(0.3)
        thread_context = get_thread_context()
        if thread_context is not None:
            channel = thread_context.channel_id
            say(f"Ah, you're referring to <#{channel}>! Do you need help with the channel?")
        else:
            say("Here you are! blah-blah-blah...")
    except Exception as e:
        logger.exception(f"Failed to respond to an inquiry: {e}")
        say(f":warning: Sorry, something went wrong during processing your request (error: {e})")

app.use(assistant)

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.

[codecov]

Codecov Report

Attention: Patch coverage is 81.87067% with 157 lines in your changes missing coverage. Please review.

Project coverage is 90.85%. Comparing base (56d5ca3) to head (d0635f1).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
slack_bolt/middleware/assistant/assistant.py	65.90%	45 Missing ⚠️
slack_bolt/middleware/assistant/async_assistant.py	65.64%	45 Missing ⚠️
...xt/assistant/thread_context_store/file/__init__.py	37.03%	17 Missing ⚠️
...istant/thread_context_store/default_async_store.py	74.07%	7 Missing ⚠️
...xt/assistant/thread_context_store/default_store.py	74.07%	7 Missing ⚠️
slack_bolt/request/payload_utils.py	78.57%	6 Missing ⚠️
slack_bolt/request/internals.py	78.94%	4 Missing ⚠️
...lack_bolt/context/assistant/assistant_utilities.py	95.91%	2 Missing ⚠️
...olt/context/assistant/async_assistant_utilities.py	96.07%	2 Missing ⚠️
...text/assistant/thread_context_store/async_store.py	71.42%	2 Missing ⚠️
... and 15 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1162      +/-   ##
==========================================
- Coverage   92.02%   90.85%   -1.17%     
==========================================
  Files         195      221      +26     
  Lines        6631     7491     +860     
==========================================
+ Hits         6102     6806     +704     
- Misses        529      685     +156     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.