* Resolve JSON serialization bug in OneOf converters and organize pricing models
* Support free organizations for payment method and billing address flows
* Run dotnet format
* Add feature flag
* Further establish billing command pattern and use in PreviewTaxAmountCommand
* Add billing address models/commands/queries/tests
* Update TypeReadingJsonConverter to account for new union types
* Add payment method models/commands/queries/tests
* Add credit models/commands/queries/tests
* Add command/query registrations
* Add new endpoints to support new command model and payment functionality
* Run dotnet format
* Add InjectUserAttribute for easier AccountBillilngVNextController handling
* Add InjectOrganizationAttribute for easier OrganizationBillingVNextController handling
* Add InjectProviderAttribute for easier ProviderBillingVNextController handling
* Add XML documentation for billing command pipeline
* Fix StripeConstants post-nullability
* More nullability cleanup
* Run dotnet format
* Set automatic tax to enabled and tax exempt to reverse where applicable when ff is on
* Fix and add tests
* Run dotnet format
* Run dotnet format
* PM-21745: Resolve defect
* PM-21770: Resolve defect
* Run dotnet format'
* [NO LOGIC] [PM-21104] Organize Core.Billing tax code
* Add PreviewTaxAmountCommand and expose through TaxController
* Add PreviewTaxAmountCommandTests
* Run dotnet format
