Respect fallbackPollIntervalInMs configuration

[alexlopashev]

#1564 introduced fallbackPollIntervalInMs configuration property to allow customization of schema updates polling period.

UplinkSupergraphManager validates this value and sets a floor value of 10 seconds to prevent unnecessary load of Uplink API.

However, initial value of pollIntervalMs can be overridden by SupergraphSdlUpdate response data, particularly these lines (https://github.com/apollographql/federation/blob/main/gateway-js/src/supergraphManagers/UplinkSupergraphManager/index.ts#L230):

if (result?.minDelaySeconds) {
    this.pollIntervalMs = result.minDelaySeconds * 1000;
}

So far it looks like minDelaySeconds is always set to be 30 seconds. This behavior prevents us to define a larger update window, and probably is a simple oversight.

We suggest updating lines in question to:

if (result?.minDelaySeconds) {
    this.pollIntervalMs = Math.max(this.pollIntervalMs, result.minDelaySeconds * 1000);
}

This way we can define larger update windows, while still respecting semantics of minDelaySeconds.

Additionally, I wonder if Apollo team sees value in allowing disabling schema updates altogether, e.g. by providing fallbackPollIntervalInMs < 0. This would be handy for our experiments, but might not be as useful for majority of users. with a workaround of providing a very large value instead.

One important note: because setTimeout is used to schedule polling requests, it might be useful to document that fallbackPollIntervalInMs must not exceed value of 2,147,483,647 ms (about 24.8 days): https://developer.mozilla.org/en-US/docs/Web/API/setTimeout#maximum_delay_value