* 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
* Remove gRPC and convert PricingClient to HttpClient wrapper
* Add PlanType.GetProductTier extension
Many instances of StaticStore use are just to get the ProductTierType of a PlanType, but this can be derived from the PlanType itself without having to fetch the entire plan.
* Remove invocations of the StaticStore in non-Test code
* Deprecate StaticStore entry points
* Run dotnet format
* Matt's feedback
* Run dotnet format
* Rui's feedback
* Run dotnet format
* Replacements since approval
* Run dotnet format
* Add a Pricing Client and mapping layer back to StaticStore.Plan
* Run dotnet format
* Temporarily remove service registration to forego any unforseen side effects
* Run dotnet format
