feat(apisix): separate inline upstream

[LiteSun]

Description

Separate inline upstream in apisix backend as discussed in #319

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible

[CLAassistant]

All committers have signed the CLA.

[bzp2010]

Please ensure that code is always formatted by Prettier and avoid making changes that serve no practical purpose.

[bzp2010]

Given that service is a special case, creating an operateService function for it is a better choice. Let other resources continue using the simple operate function, while services with specific upstream expansion logic use a separate function.

private operate(event: ADCSDK.Event) {
   // keep original codes
}

// handle only event for service
private operateService(event: ADCSDK.event) {
  const operateWithRetry = (op) => defer(op).pipe(retry({count: 3, delay: 100/* or fn */}));
  if (event.type === ADCSDK.EventType.DELETE) {
    return from([() => this.client.delete("/apisix/admin/services/xxx"), () => this.client.delete("/apisix/admin/upstreams/xxx")]).pipe(
      concatMap((op) => operateWithRetry(op))
    )
  } else {
    return from([() => this.client.put("/apisix/admin/upstreams/xxx"), () => this.client.put("/apisix/admin/services/xxx")]).pipe(
      concatMap((op) => operateWithRetry(op))
    )
  }
}