Currently sessions are never removed from memory, and we prevent the server from running out of memory by externally restarting it every Sunday morning.

Instead of this, we can automatically remove sessions from the ShareDB some time after the last user disconnects.

Implementation:

1. Track the number of users connected to each session by binding to the WebSocket connect/disconnect events. Also track the last disconnect time.
2. Every hour or so, remove sessions that have no users and whose last disconnection time is more than an hour old.

source-academy/sharedb-ace-backend

Known high severity security vulnerability detected in lodash < 4.17.13 defined in package-lock.json.package-lock.json update suggested: lodash ~> 4.17.13. | Known high severity security vulnerability detected in lodash < 4.17.13 defined in package-lock.json. | package-lock.json update suggested: lodash ~> 4.17.13.
Known high severity security vulnerability detected in lodash < 4.17.13 defined in package-lock.json.
package-lock.json update suggested: lodash ~> 4.17.13.

source-academy/sharedb-ace-backend

Known high severity security vulnerability detected in lodash < 4.17.13 defined in yarn.lock.yarn.lock update suggested: lodash ~> 4.17.13. | Known high severity security vulnerability detected in lodash < 4.17.13 defined in yarn.lock. | yarn.lock update suggested: lodash ~> 4.17.13.
Known high severity security vulnerability detected in lodash < 4.17.13 defined in yarn.lock.
yarn.lock update suggested: lodash ~> 4.17.13.

source-academy/sharedb-ace-backend

Known high severity security vulnerability detected in ws >= 0.2.6, < 3.3.1defined in yarn.lock.yarn.lock update suggested: ws ~> 3.3.1. | Known high severity security vulnerability detected in ws >= 0.2.6, < 3.3.1defined in yarn.lock. | yarn.lock update suggested: ws ~> 3.3.1.
Known high severity security vulnerability detected in ws >= 0.2.6, < 3.3.1defined in yarn.lock.
yarn.lock update suggested: ws ~> 3.3.1.

GET /gists/latest shouldn't cause a new instance to be created. Need to fix the frontend to POST /gists/new instead.