New Features

• feat(firestore): Upgrade google-cloud-firestore to support Firestore Multi Database (#827)
• feat: Support passing google.auth typed credentials in initialize_app() (#821)
• feat(firestore): Add Firestore Multi Database Support (#818)

Miscellaneous

• [chore] Release 6.6.0 Take 2 (#830)
• [chore] Release 6.6.0 (#829)
• chore: Add X-Goog-Api-Client metric header to requests (#826)
• chore: Create dependabot.yml (#820)
• [chore] Bump cachecontrol (#819)
• chore: Update actions/upload-artifact (#812)
• chore(deps): bump actions/download-artifact in /.github/workflows (#810)
• chore: Remove Python 3.7 from workflows (#806)
• Fix link to requests.Response in FirebaseError. (#800)
• chore: Update integration test resources (#796)