[RESTDataSource] refactor to allow overridding the Error class

[eturino]

for example if we want to create a NotFoundError that will be used when receiving 404s. This way we need to override the bare minimum like

class MyDataSource extends RESTDataSource {
  protected errorBaseFromResponseAndMessage(response: Response, message: string): ApolloError {
    if (response.status === 401) return new NotFoundError(message);

    return super.errorBaseFromResponseAndMessage(response, message);
  }
}

Also adding it in the RemoteGraphQLDataSource since it has the same code as RESTDataSource, for symmetry purposes.

[eturino]

@abernix can I ask the reason for closing it? Is there anything I can do to help get it along?

[eturino]

Ah! I just saw the comment at the end of #4302
I can reopen it.

[abernix]

Okay, so the automated process was able to re-open all but five of the PRs, and this was one of them. Reason being (from the GitHub interface): The branch was force-pushed or recreated.

So I could have re-opened this, but since you opened a new one, that one has to be re-opened instead. 🤷

All good! I'll re-open the other one (which I already closed). Sorry for the noise!