feat: chat stream helper

[srtaalej]

This PR adds a helper to the chat streaming methods

ChatStreamHelper stream = (req -> req.
    .channel("C0123456789")
    .threadTs("1700000001.123456")
    .recipientTeamId("T0123456789")
    .recipientUserId("U0123456789")
    .bufferSize(100));
stream.append("**hello wo");
stream.append("rld!**");
ChatStopStreamResponse response = stream.stop();

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

• bolt (Bolt for Java)
• bolt-{sub modules} (Bolt for Java - optional modules)
• slack-api-client (Slack API Clients)
• slack-api-model (Slack API Data Models)
• slack-api-*-kotlin-extension (Kotlin Extensions for Slack API Clients)
• slack-app-backend (The primitive layer of Bolt for Java)

Requirements

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

[codecov]

Codecov Report

❌ Patch coverage is 75.14451% with 43 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.43%. Comparing base (f48758d) to head (beb1b92).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...a/com/slack/api/methods/AsyncChatStreamHelper.java	71.59%	21 Missing and 4 partials ⚠️
...n/java/com/slack/api/methods/ChatStreamHelper.java	79.22%	12 Missing and 4 partials ⚠️
...om/slack/api/methods/SlackChatStreamException.java	66.66%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1545      +/-   ##
============================================
+ Coverage     73.32%   73.43%   +0.10%     
- Complexity     4515     4549      +34     
============================================
  Files           477      480       +3     
  Lines         14274    14447     +173     
  Branches       1487     1498      +11     
============================================
+ Hits          10467    10609     +142     
- Misses         2917     2941      +24     
- Partials        890      897       +7     

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[zimeg]

@srtaalej This is awesome to review and test! Thanks for putting it together 👾 ✨

I'm leaving a few comments around how we might surface this for the web client that might make it easier to use in calling code, similar to other SDKs, but please let me know if language limits these idea 🙏

[zimeg]

👁️‍🗨️ thought: This works well but I'm wondering if it's possible to attach the chat stream helper to the client for an implementation similar to files upload?

String token = System.getenv("SLACK_BOT_TOKEN");
var client = Slack.getInstance().methods(token);
client.filesUploadV2(req -> req.content("greetings!").channel("C01223456789"));

[zimeg]

⭐ praise: Nice! I forget if casting between related types might also work here but I think the explicit setting is most clear.