`oauth-kit/client.ts` builds a provider's consent URL, code exchange,
refresh and deauthorization from a declaration of what differs: endpoints
and scope, client authentication (form or HTTP Basic, with or without the
client id beside it), the fields a grant adds, how an answer is classified
and the refusal named, the error type, and where the token sits in the
body. The seven hand-written copies of the redirect URI, authorization URL,
token post, Basic header and PKCE pair are gone; each provider keeps an
`oauth.ts` with its declaration.
Shared behaviour is now uniform: a 2xx without a token object (an empty or
non-JSON body) is a transient `empty_token_body` failure for every
provider. WHOOP, Strava and Google Health used to return null, and
Withings threw an unclassified SyntaxError; the OAuth wire golden records
exactly these lines changing and nothing else. Oura's live/legacy endpoint
fallback, Google's invalid_grant lift, Strava's Fault summary and Fitbit's
errorType are declared per provider.
Marc-André Bombeck