retryableMethods property
HTTP methods that are eligible for automatic retry.
Defaults to the idempotent methods per RFC 7231 ยง4.2.2:
{GET, HEAD, OPTIONS, TRACE, PUT, DELETE}. POST and PATCH are
excluded by default because replaying them is unsafe: a 5xx returned
after the server already committed (e.g. a gateway 502/504 timeout
on a payment) would otherwise produce a duplicate (double charge).
Comparison is case-insensitive; values must be upper-case.
To retry a specific non-idempotent request that is provably safe to
replay (e.g. a POST carrying an Idempotency-Key), prefer the
per-request opt-in RequestOptions.forceRetry() over widening this set,
which would re-enable retry for every request of that method.
Implementation
final Set<String> retryableMethods;