Fix: Feature usage chart pagination

[jcscottiii]

Background:

When backfilling usage data, the feature usage chart displayed only a few data points, not the complete set. Network inspection revealed that multiple pages of data were successfully retrieved.

Repro:

1. Navigate to: https://website-webstatus-dev.corp.goog/features/flexbox?showUsageChart
2. Examine the usage chart. You will see the oldest page of results are only shown. Not all of the points. But if you examine the network tab in DevTools, you will see multiple calls were made.

Solution:

This change aligns the feature usage chart pagination with the feature support chart's implementation:

webstatus.dev/frontend/src/static/js/components/webstatus-feature-page.ts

Lines 621 to 650 in b84a9ac

	async _fetchFeatureSupportData(
	apiClient: APIClient,
	featureId: string,
	startDate: Date,
	endDate: Date,
	) {
	if (typeof apiClient !== 'object') return;
	this.featureSupportChartDataObj = this.createFeatureSupportDataFromMap();
	const channel = STABLE_CHANNEL;
	const promises = ALL_BROWSERS.map(async browser => {
	for await (const page of apiClient.getFeatureStatsByBrowserAndChannel(
	featureId,
	browser,
	channel,
	startDate,
	endDate,
	)) {
	// Append the new data to existing data
	const existingData =
	this.featureSupport.get(featureSupportKey(browser, channel)) || [];
	this.featureSupport.set(featureSupportKey(browser, channel), [
	...existingData,
	...page,
	]);
	this.featureSupportChartDataObj =
	this.createFeatureSupportDataFromMap();
	}
	});

Testing:

Comprehensive unit tests will be included with the refactor outlined in #964.

To validate the pagination logic, this commit increases the number of data points displayed to over 100, enabling testing through Playwright. To optimize Playwright test performance, the initial data load specifically filters for the feature used in the feature page test, mitigating delays associated with loading excessive fake data.

Other changes

• Add more logging to the fake data script

[DanielRyanSmith]

Thanks for catching this James!