[Azure Billing] Update forecast api metrics interval

[muthu-mps]

• Bug

What does this PR do?

Fixes #35633

Why is it important?

The proposed change fetches the forecast data for the next 30 days from the current day(-2). As of today, the forecast metrics is fetched from the beginning of the month to the end of the month. Considering the fact that this API returns the actual data to consolidate the cost we are adjusting the start date to current day - 2 days.

How to test this PR locally

• Enable the Azure billing metrics module.
• Perform the configuration
• Verify the billing metrics forecast API fetches metrics from yesterday and for next 30 days.
• Ensure there the other metrics are getting loaded in the dashboards.

Related issues

• Closes Azure Billing integration - start/end interval in Forecast API call causes 2 day records gap at the end of each month #35633

Screenshots

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[zmoog]

The Forecast API returns two kinds of data in the same response:

• actual data, the consolidated past costs.
• forecast data, the forecast of future costs.

By changing the interval to -1 day and +30 days, we are getting the forecast data but missing the actual data. This happens because actual data are past costs that require some time to consolidate.

Here's the actual response using the PR code:

Here's a quick test with -2 days instead of -1 days, so we give actual data to consolidate:

[zmoog]

We also need to update the CHANGELOG.next.asciidoc with and entry for this bug fix.

[zmoog]

I tested this change, and it looks good.

On each collection, we're now getting:

• one day of actual costs
• 30 days of forecast costs

So we expect the integration to accumulate actual costs over time and have a 30 days outlook of forecasted costs.

[muthu-mps]

I tested this change, and it looks good.

On each collection, we're now getting:

• one day of actual costs
• 30 days of forecast costs

So we expect the integration to accumulate actual costs over time and have a 30 days outlook of forecasted costs.

Thanks @zmoog !