Related Slack thread

Problem

At the moment we have additionalFields: false in the experimentalFeatures section in the sourcegraph settings json file. This has two implications

• You can't store any additional fields in the experimentalFeatures section (you see an error if you try to save settings with not allowed fields there)
• Settings editor highlights these not allowed fields in the UI

But this system forces us to have all experimental feature flags all time because we can just delete them because then our settings will become invalid (see point 1 above)

So in order to solve this problem for now we need to remove this additionalFields: false from the setting json schema (and also remove the deprecated features flags from the schema since it will become possible).

/cc @Joelkw @felixfbecker @vovakulikov