This reduces the overall amount of LoC that imports take up in our
codebase by almost 100.
It also makes merge-conflicts less likely because there is less
grouping together of imports that may lead to layout changes which
in turn can cause merge conflicts.
This allows us to use .context instead of .map_err when calling
`latest_rate()`. For the static rate module, we simply fill in
`Infallible` which is actually better suited because it describes
that we are never using this error.
Note that because we are using `watch` channel, only a reference to the
channel value can be returned.
Hence, using custom Error that can be cloned to be able to
pass `Result` through the channel.
