[PM-21881] Manage payment details outside of checkout (#6032)

* 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

test/Api.Test/Billing/Attributes/InjectOrganizationAttributeTests.cs

@@ -0,0 +1,132 @@
+using Bit.Api.Billing.Attributes;
+using Bit.Core.AdminConsole.Entities;
+using Bit.Core.Models.Api;
+using Bit.Core.Repositories;
+using Microsoft.AspNetCore.Http;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.AspNetCore.Mvc.Abstractions;
+using Microsoft.AspNetCore.Mvc.Filters;
+using Microsoft.AspNetCore.Mvc.ModelBinding;
+using Microsoft.AspNetCore.Routing;
+using Microsoft.Extensions.DependencyInjection;
+using NSubstitute;
+using Xunit;
+
+namespace Bit.Api.Test.Billing.Attributes;
+
+public class InjectOrganizationAttributeTests
+{
+    private readonly IOrganizationRepository _organizationRepository;
+    private readonly ActionExecutionDelegate _next;
+    private readonly ActionExecutingContext _context;
+    private readonly Organization _organization;
+    private readonly Guid _organizationId;
+
+    public InjectOrganizationAttributeTests()
+    {
+        _organizationRepository = Substitute.For<IOrganizationRepository>();
+        _organizationId = Guid.NewGuid();
+        _organization = new Organization { Id = _organizationId };
+
+        var httpContext = new DefaultHttpContext();
+        var services = new ServiceCollection();
+        services.AddScoped(_ => _organizationRepository);
+        httpContext.RequestServices = services.BuildServiceProvider();
+
+        var routeData = new RouteData { Values = { ["organizationId"] = _organizationId.ToString() } };
+
+        var actionContext = new ActionContext(
+            httpContext,
+            routeData,
+            new ActionDescriptor(),
+            new ModelStateDictionary()
+        );
+
+        _next = () => Task.FromResult(new ActionExecutedContext(
+            actionContext,
+            new List<IFilterMetadata>(),
+            new object()));
+
+        _context = new ActionExecutingContext(
+            actionContext,
+            new List<IFilterMetadata>(),
+            new Dictionary<string, object>(),
+            new object());
+    }
+
+    [Fact]
+    public async Task OnActionExecutionAsync_WithExistingOrganization_InjectsOrganization()
+    {
+        var attribute = new InjectOrganizationAttribute();
+        _organizationRepository.GetByIdAsync(_organizationId)
+            .Returns(_organization);
+
+        var parameter = new ParameterDescriptor
+        {
+            Name = "organization",
+            ParameterType = typeof(Organization)
+        };
+        _context.ActionDescriptor.Parameters = [parameter];
+
+        await attribute.OnActionExecutionAsync(_context, _next);
+
+        Assert.Equal(_organization, _context.ActionArguments["organization"]);
+    }
+
+    [Fact]
+    public async Task OnActionExecutionAsync_WithNonExistentOrganization_ReturnsNotFound()
+    {
+        var attribute = new InjectOrganizationAttribute();
+        _organizationRepository.GetByIdAsync(_organizationId)
+            .Returns((Organization)null);
+
+        await attribute.OnActionExecutionAsync(_context, _next);
+
+        Assert.IsType<NotFoundObjectResult>(_context.Result);
+        var result = (NotFoundObjectResult)_context.Result;
+        Assert.IsType<ErrorResponseModel>(result.Value);
+        Assert.Equal("Organization not found.", ((ErrorResponseModel)result.Value).Message);
+    }
+
+    [Fact]
+    public async Task OnActionExecutionAsync_WithInvalidOrganizationId_ReturnsBadRequest()
+    {
+        var attribute = new InjectOrganizationAttribute();
+        _context.RouteData.Values["organizationId"] = "not-a-guid";
+
+        await attribute.OnActionExecutionAsync(_context, _next);
+
+        Assert.IsType<BadRequestObjectResult>(_context.Result);
+        var result = (BadRequestObjectResult)_context.Result;
+        Assert.IsType<ErrorResponseModel>(result.Value);
+        Assert.Equal("Route parameter 'organizationId' is missing or invalid.", ((ErrorResponseModel)result.Value).Message);
+    }
+
+    [Fact]
+    public async Task OnActionExecutionAsync_WithMissingOrganizationId_ReturnsBadRequest()
+    {
+        var attribute = new InjectOrganizationAttribute();
+        _context.RouteData.Values.Clear();
+
+        await attribute.OnActionExecutionAsync(_context, _next);
+
+        Assert.IsType<BadRequestObjectResult>(_context.Result);
+        var result = (BadRequestObjectResult)_context.Result;
+        Assert.IsType<ErrorResponseModel>(result.Value);
+        Assert.Equal("Route parameter 'organizationId' is missing or invalid.", ((ErrorResponseModel)result.Value).Message);
+    }
+
+    [Fact]
+    public async Task OnActionExecutionAsync_WithoutOrganizationParameter_ContinuesExecution()
+    {
+        var attribute = new InjectOrganizationAttribute();
+        _organizationRepository.GetByIdAsync(_organizationId)
+            .Returns(_organization);
+
+        _context.ActionDescriptor.Parameters = Array.Empty<ParameterDescriptor>();
+
+        await attribute.OnActionExecutionAsync(_context, _next);
+
+        Assert.Empty(_context.ActionArguments);
+    }
+}