* Use `Position` everywhere instead of latitude/longitude float values
* Implement `Partial`, `Eq` and `Hash` for `Position` so it can
part of a cache key
* Drop the `cache_key` helper function
* Rename the `address_position` function to `resolve_address`
* Add methods on `Position` for formatting latitude/longitude with
a given precision (used for URL parameters in providers)
* Also cache address geocoding requests to OSM Nomatim!
* Use the `cached` crate for an easy implementation
* Add the `cache_key` helper function to deal with floats being annoying
* Cache Buienradar get request for 5 minutes (per position/metric)
* Cache Luchtmeetnet get request for 5 minutes (per position/metric)
* Note the `Item` structs need to implement `Clone` now because
the cache will own them and Rocket will want a copy too
* Add the `csv` crate as a dependency
* Use the `Row` struct as intermediate object
* Turn the `parse_value` function into the `convert_value` function that
cannot fail
This makes the response time way more snappy when the maps thread
is updating its cache.
* Move the `MapsHandle` type to the `maps` module
* SWitch to using the standard library mutex
* Split refresh methods into retrieval methods that don't need the lock
and check timestamp & update methods that only need it shortly
* Introduce the `MapsRefresh` trait and implement it for `MapsHandle`
* Reorder some methods for clarity
* Small documentation fixes
* Replace the lazy `once_cell` by a maps handle type
* Use Rocket's managed state to manage a handle
* Ensure that the handlers have access to it
* Pass another handle to the maps updater loop
* Try to keep the lock as short as possible
Still, long downloads block the lock. Add a FIXME to refactor this
so the lock is only taken when updating the maps fields.
Paul van Tilburg
