RestHeaders typedef

RestHeaders = Future<Map<String, String>> Function(RestRequest request)

Builds the headers every call carries.

Called once per request, so it can read a credential that has just been renewed, sign a payload, or stamp a request identifier. Whatever it returns is merged under RestRequest.headers, which therefore always wins.

Nothing about authentication is assumed here: an adapter that sends Authorization: Bearer writes that, one that sends an API key header writes that instead.

Implementation

typedef RestHeaders = Future<Map<String, String>> Function(RestRequest request);