pubsub - A simple pub/sub service over HTTP
- `/api/pubsub/`                GET   Get help. Returns: this help message.
- `/api/pubsub/ping`            GET   Check status. Returns: `Pong`
- `/api/pubsub/topic/new`       GET   Create new topic. Returns: `{"id": <id>, "pub_key": <pub_key>, "sub_key": <sub_key>}`
- `/api/pubsub/topic/pub/<id>`  POST  Post message to topic. Requires header: `{"pub_key": <pub_key>}`
- `/api/pubsub/topic/sub/<id>`  GET   Get (and remove) oldest message from topic. Requires header: `{"sub_key": <sub_key>}`.