✨ Add watch_logs API operation

[linkdd]

Decision Record

In order to improve inter-operability, we add a new watch_logs API operation which implements Sever-Sent Events, as a streaming response with text/event-stream content type.

Users are able to watch logs of a specific stream in real time:

$ curl -H "Authorization: Bearer <token>" http://localhost:5080/api/v1/streams/{stream}/logs/watch
id: <log key>
event: log
data: {"timestamp": "...", "fields": {...}}

...

Changes

• ✨ Add LogNotifier background task
• ✨ Make pipelines send a message to the LogNotifier when ingesting a log into a stream
• ✨ Add watch_logs API operation which subscribes to a stream via the LogNotifier

License Agreement

• I guarantee that I have the rights on the code submitted in this PR
• I accept that this contribution will be released under the terms of the MIT License