Turns a replica's refusal into an answer the caller can act on. The retry is safe because the
refusal throws before the inner capability runs; didMutate() is checked, and a true reading
downgrades to a 500. 421 not 503: this object will refuse the request forever.
Turns a replica's refusal into an answer the caller can act on. The retry is safe because the refusal throws before the inner capability runs;
didMutate()is checked, and a true reading downgrades to a 500. 421 not 503: this object will refuse the request forever.