Expose 'trace' in RESTDataSource as a protected method

[eduardoramirez]

Expose RESTDataSource.trace as a protected method so implementers can override the default behavior. This is useful for instrumenting a data-source with tracing logic.

TODO:

• Update CHANGELOG.md with your change (include reference to issue & this PR)
• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests and linter rules pass

[slagiewka]

@martijnwalraven hey, does the team have any thoughts on that?

[Guillaume-Mayer]

I was about to submit something similar:

  private async trace<TResult>(
    label: string,
    fn: () => Promise<TResult>,
  ): Promise<TResult> {
    if (this.shouldTraceLog()) {
      // We're not using console.time because that isn't supported on Cloudflare
      const startTime = Date.now();
      try {
        return await fn();
      } finally {
        const duration = Date.now() - startTime;
        this.traceLog(label, duration);
      }
    } else {
      return fn();
    }
  }

  protected shouldTraceLog(): boolean {
    return process && process.env && process.env.NODE_ENV === 'development';
  }

  protected async traceLog(label: string, duration: number): Promise<void> {
    console.log(`${label} (${duration}ms)`);
  }

I'd like to be able to activate the trace independently of NODE_ENV.
Ideally I would like to include the cache status (HIT/MISS) in the trace, not sure how.