feat: pass through billing query params

[zlwaterfield]

Changes

We support include_forecasting in billing now so we should add pass through support.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Does this work well for both Cloud and self-hosted?

It doesn't have an impact.

How did you test this code?

Added a test

[sentry-io]

Suspect Issues

This pull request was deployed and Sentry observed the following issues:

• ‼️ Exception: ('Billing service returned bad status code: 504', 'body:', '\r\n<title>504 Gateway Ti... /api/billing/ View Issue
• ‼️ Organization.DoesNotExist: Organization matching query does not exist. /api/billing/ View Issue
• ‼️ ConnectionError: HTTPSConnectionPool(host='billing.posthog.com', port=443): Max retries exceeded with url: /api/bi... /api/billing/ View Issue
• ‼️ OperationalError: consuming input failed: server closed the connection unexpectedly /api/billing/ View Issue
• ‼️ Exception: ('Billing service returned bad status code: 500', 'body:', {'type': 'server_error', 'code': 'erro... /api/billing/ View Issue

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