chore(slack): Remove redundant thread ID generation

[0xRichardH]

Thread ID Generation Inconsistency:

There are two different thread ID generation approaches in the handle_message function. The first one is immediately overwritten by the second:

# backend/chainlit/slack/app.py

- thread_id = str(
-     uuid.uuid5(
-         uuid.NAMESPACE_DNS,
-         message["channel"] + datetime.today().strftime("%Y-%m-%d"),
-     )
- )
 thread_ts = message.get("thread_ts", message["ts"])
 thread_id = str(uuid.uuid5(uuid.NAMESPACE_DNS, thread_ts))

[willydouhard]

do we want to keep the per day segmentation? If not this means that we will get one thread per channel which can grow pretty fast.

[0xRichardH]

thread_ts is a thread message key, which means we will get one chainlit thread per Slack thread.

https://api.slack.com/messaging/retrieving

[willydouhard]

LGTM