Sends token-endpoint requests (authorization-code exchange and refresh) with the per-provider options recorded from the Nango catalog in provider metadata (see Tango.Schemas.Provider.catalog_metadata/1).

Without those options the request is the oauth2 library default: client credentials in an HTTP Basic header (plus client_id in the body for the code exchange) and a form-encoded body. The options follow Nango (packages/shared/lib/clients/oauth2.client.ts and packages/server/lib/controllers/oauth.controller.ts):

• "token_request_auth_method" => "basic" - Basic header, and the client credentials also in the body
• "authorization_method" => "header" - client credentials only in the Basic header
• "body_format" => "json" - JSON body instead of a form
• "token_params" - extra params for the code exchange; also used for refresh when there are no "refresh_params"
• "refresh_params" - extra params for the refresh

Extra params never override the grant type, code, redirect URI, PKCE verifier, or refresh token Tango sets.