ndi.cloud.api.implementation.files.signedURLFileMap

 SIGNEDURLFILEMAP Build a uid -> signed URL map, preserving the true uids.

    FILEMAP = ndi.cloud.api.implementation.files.SIGNEDURLFILEMAP(DECODEDFILES, RAWPAYLOAD)

    The signed-url-set endpoints return a JSON object whose keys are DID file
    uids:

        "files": { "4192a3c0dd1b4e00_3fe8a1b2c3d4e5f6": "https://...", ... }

    MATLAB decodes a JSON object into a struct, and a struct field name cannot
    begin with a digit. A did.ido uid is NUM2HEX(<serial date>) '_'
    NUM2HEX(<random>), so it is 16 hex digits, an underscore, and 16 more hex
    digits -- and it begins with a digit far more often than not. JSONDECODE
    silently renames those fields (prefixing an 'x'), so reading the uids back
    off the decoded struct would hand callers uids that do not exist.

    The field ORDER, however, survives decoding. So this function takes the
    values from the decoded struct (letting JSONDECODE handle string escaping
    in the URLs) and the keys from the raw payload text (which still has the
    uids verbatim), and zips them together.

    Inputs:
        decodedFiles - The decoded `files` value: a struct whose fields are the
                       (possibly renamed) uids, or [] / empty struct if the page
                       carried no files.
        rawPayload   - The raw response payload (uint8 or char). Obtain it by
                       sending the request with
                       matlab.net.http.HTTPOptions('SavePayload', true) and
                       reading apiResponse.Body.Payload.

    Outputs:
        fileMap      - A containers.Map from uid (char) to signed URL (char).
                       Empty map when there are no files. ValueType is
                       'any' because containers.Map requires scalar values for
                       any other ValueType, and a URL is a char array.

    If the raw payload cannot be scanned (empty, or a key count that disagrees
    with the decoded struct), this errors rather than returning uids that were
    silently renamed. A wrong uid is worse than a failed call: it would send
    the caller to download a file that does not exist, or -- if it happened to
    collide -- the wrong file.

    See also: ndi.cloud.api.files.getSignedURLSet