OptionalheadersMerged over the static headers.
OptionalinitPassed through to fetch - credentials, mode, cache, signal, ...
OptionalmethodReplaces the verb this operation would otherwise use.
OptionalqueryMerged over the static query parameters.
Per-request adjustments, resolved at call time.
Returned from RestDataSourceOptions.configureRequest, which may be async - so a token can be awaited from a refresh call rather than captured when the source was constructed.