Allow slash command responses to be cached

[MattIPv4]

👋 Small little idea to reduce load for developers and Discord potentially, and improve response times for end users using slash commands.

It'd be awesome if developers could include a cache ttl in their slash command responses, so that Discord can store that response for that period of time and reuse it if the same command is run again.

E.g. DNS over Discord returns DNS responses, and these already have a known ttl, so it'd be great if I could tell Discord to honour that before asking me again for an updated response with new DNS data. Or, for commands that have static content like an invite command or a privacy policy command, it'd be great if I could set a super long cache ttl on that so Discord only needs to ask me for it once and then just serves the cached response to subsequent command uses.

To further this idea, it'd be even cooler if there was also an optional cache scope. Say for example, the cached response is only valid for the current user, or only in the current thread/channel/guild.