[BY-3620]: Make retry work with Node's fetch, and only retry safe requests

[paulambanks]

Before

• Retry was off by default, and no Beyonk app enabled it.
• If enabled, it only matched e.code. Node's fetch reports network errors as TypeError: fetch failed with the code on e.cause, so retries never happened.
• If it had matched, it would have retried any method, including writes.

After

• It matches the code on the error or on its cause, so resets (ECONNRESET) from Node's fetch are now retried.
• Only GET, HEAD and OPTIONS are retried by default, so a write that may have reached the server is never sent twice. Endpoints that are safe to repeat can opt in with the new methods option.
• It's still off by default. Nothing changes for an app until it sets retry.

Impact: no existing app changes behaviour. Apps that enable retry: { attempts: 2, errors: ['ECONNRESET'] } get one automatic retry on reset GET requests.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@beyonk/http@48

commit: a813f40

[alexdilley]

Can't tell if we want to actually retry on ECONNRESET as a library default or not.