Currently, unless a locale is present in the URL search params, the
locale context is instantiated using the default locale until prefs load
in client-side. This causes the locale selector to briefly render in
with the incorrect (default) locale before being replaced by the proper
locale of the request. For example, if the default locale is `en`, and
the page is requested in `es`, the locale selector will flash with
English before changing to the correct locale, even though the page data
itself is properly loaded in Spanish. This is especially evident within
slow networks.
The fix is to query the user's locale preference server-side and thread
it into the locale provider to initialize state. Because search params
are not available within server layouts, we cannot pass the locale param
in the same way, so we rely on the provider itself to read them from the
`useSearchParams` hook. If present, this takes precedence over the
user's preference if it exists.
Since the root page also queries the user's locale preference to
determine the proper locale across navigation, we use React's cache
function to dedupe these function calls and ensure only a single query
is made to the db for each request.
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