add a README for the hub service

Signed-off-by: jkoberg <[email protected]>

services/hub/README.md

@@ -0,0 +1,14 @@
+# Hub Service
+
+The hub service provides `server sent events` (`sse`) functionality to clients
+
+## Subscribing
+
+A client can use the `hub/sse` endpoint to subscribe to events. It will open an http connection for the server to send events.
+These events can inform the client about different changes on the server, for example: file uploads, shares, space memberships, ...
+See `Available Events` for details
+
+## Available Events
+For complete and up-to-date list of available events see `pkg/service/events.go`
+
+For starters the `hub` service only serves the `UploadReady` event which is emitted when a files postprocessing is finished and the file is ready to work with