When a file cannot be retrieved any longer, we send a redirect to the previous locations. As we usually enable a different render host, Rails sees this redirect as a redirect to another host (from the render host to the main CodeOcean host).
* Remove `send_stream` method pulled in before upgrading Rails
* Remove spring, it is no longer included by default for new apps
* Remove deprecated options from environments
* Remove old asset paths and workarounds no longer needed
* Remove unnecessary `OAUTH_10_SUPPORT` const, LTI still uses OAuth 1.0
* Dump schema with new defaults (and specify precision for timestamps where needed)
