Cache response from yr.no

[Erb3]

Added in #354, the weather source is yr.no. Yr requires that the responses from their API are cached. We should narrow down the coordinates to a bigger area, then cache it in Redis for a few hours. Redis supports expiry of values, which is nice.

I've separated it into smaller tasks:

• Make redis available to weather.ts route
• Make sure redis is still available to middleware.ts
• Remove a few decimals from the coordinates for them to be less accurate and cover a bigger area
• Store the coordinates and summary, max_temp and min_temp in redis. Expire after a few hours.
• On request to weather API, check if we have a cached version of the response, if so return that
• Document this

To be clear, I am not suggesting that all of these changes have their own PR, all of them should be in one PR.