New services/project_events package marshals typed payloads to JSON,
wraps them in SSE events named project-board.{project_id}, and fans
them out via the eventsource manager to every connected user that
has read access to the project. Each Publish* helper runs the
broadcast in a goroutine so request handlers stay responsive.
Includes WithSessionTag / SessionTagFromContext for propagating an
X-Session-Tag value down to the publisher (so the originating browser
tab can suppress its own echo).
Unit tests cover event-name format, payload JSON shape, session-tag
propagation, the connected-uids access filter, and the broadcast
fan-out path.
Oleks
3c831efc0c