In internal/reader/handler/handler.go:RefreshFeed, there is a call to
store.UserByID pretty early, which is only used for
originalFeed.WithTranslatedErrorMessage(localizedError.Translate(user.Language)
Its only other usage is in processor.ProcessFeedEntries(store, originalFeed,
user, forceRefresh), which is pretty late in RefreshFeed, and only called if
there are new items in the feed. It makes sense to only fetch the user's
language if the error localization function is used.
Calls to `store.UserByID` take around 10% of the CPU time of RefreshFeed in my
profiling.
This commit also makes `processor.ProcessFeedEntries` take a `userID` instead
of a `user`, to make the code a bit more concise.
This should close#2984
637fb85de0