gleam.http.Client retry configuration lacking idempotency guard

gleam.http.Client retry configuration

The goal is to configure automatic retries for HTTP requests without risking duplicate side‑effects when the request method is not idempotent (e.g., POST, PUT with non‑idempotent payload).

Currently the Retry type attached to a gleam.http.Client request only inspects HTTP status codes and network errors; it does not evaluate the request method or body to decide whether a retry is safe.

This leaves an open decision about whether the retry API should expose an optional idempotency flag, accept a user‑provided deduplication key, or rely entirely on the caller to guarantee safety.

• Should the Retry configuration include an idempotent boolean that disables retries for unsafe methods?
• Could a deduplication key supplied by the caller be used to suppress retries that would cause duplicate writes?
• Is it preferable to document the limitation and leave duplicate‑write protection to application code?