This switches from the prehistoric EventSource API to the more modern
fetch-event-source package. That packages gives us full control over the
retries.
It also gives us the opportunity to close the event source when the
browser tab is hidden, saving resources.
Signed-off-by: Julien <roidelapluie@o11y.eu>
This commit introduces a new `/api/v1/notifications/live` endpoint that
utilizes Server-Sent Events (SSE) to stream notifications to the web UI.
This is used to display alerts such as when a configuration reload
has failed.
I opted for SSE over WebSockets because SSE is simpler to implement and
more robust for our use case. Since we only need one-way communication
from the server to the client, SSE fits perfectly without the overhead
of establishing and maintaining a two-way WebSocket connection.
When the SSE connection fails, we go back to a classic
/api/v1/notifications API endpoint.
This commit also contains the required UI changes for the new Mantine UI.
Signed-off-by: Julien <roidelapluie@o11y.eu>
