The parsed sources config section.
Validate a reference and build its URL without making a request.
Opaque document id.
Source name.
The full reference string.
Callback URL built from sources.<name>.url.
Retrieve a document. Rejects with SourceReferenceError (and sends nothing) for an invalid reference; otherwise never rejects.
The source callback client. Constructed once from the parsed
sourcesconfig (defaults applied,${ENV}already substituted at load). Each source gets its own concurrency semaphore; thetimeoutMsclock starts when a request leaves the queue, not while it waits for a slot. Callbacks do not draw from the embedding rate limiter.