[AC-2795] Add account credit & tax information to provider subscription (#4276)

* Add account credit, suspension and tax information to subscription response

* Run dotnet format'

src/Core/Billing/Models/ConsolidatedBillingSubscriptionDTO.cs

@@ -5,5 +5,5 @@ namespace Bit.Core.Billing.Models;
 public record ConsolidatedBillingSubscriptionDTO(
     List<ConfiguredProviderPlanDTO> ProviderPlans,
     Subscription Subscription,
-    DateTime? SuspensionDate,
-    DateTime? UnpaidPeriodEndDate);
+    TaxInformationDTO TaxInformation,
+    SubscriptionSuspensionDTO Suspension);

src/Core/Billing/Models/SubscriptionSuspensionDTO.cs

@@ -0,0 +1,6 @@
+namespace Bit.Core.Billing.Models;
+
+public record SubscriptionSuspensionDTO(
+    DateTime SuspensionDate,
+    DateTime UnpaidPeriodEndDate,
+    int GracePeriod);

src/Core/Billing/Utilities.cs

@@ -1,4 +1,8 @@
-namespace Bit.Core.Billing;
+using Bit.Core.Billing.Models;
+using Bit.Core.Services;
+using Stripe;
+
+namespace Bit.Core.Billing;
 
 public static class Utilities
 {
@@ -8,4 +12,67 @@ public static class Utilities
         string internalMessage = null,
         Exception innerException = null) => new("Something went wrong with your request. Please contact support.",
         internalMessage, innerException);
+
+    public static async Task<SubscriptionSuspensionDTO> GetSuspensionAsync(
+        IStripeAdapter stripeAdapter,
+        Subscription subscription)
+    {
+        if (subscription.Status is not "past_due" && subscription.Status is not "unpaid")
+        {
+            return null;
+        }
+
+        var openInvoices = await stripeAdapter.InvoiceSearchAsync(new InvoiceSearchOptions
+        {
+            Query = $"subscription:'{subscription.Id}' status:'open'"
+        });
+
+        if (openInvoices.Count == 0)
+        {
+            return null;
+        }
+
+        var currentDate = subscription.TestClock?.FrozenTime ?? DateTime.UtcNow;
+
+        switch (subscription.CollectionMethod)
+        {
+            case "charge_automatically":
+                {
+                    var firstOverdueInvoice = openInvoices
+                        .Where(invoice => invoice.PeriodEnd < currentDate && invoice.Attempted)
+                        .MinBy(invoice => invoice.Created);
+
+                    if (firstOverdueInvoice == null)
+                    {
+                        return null;
+                    }
+
+                    const int gracePeriod = 14;
+
+                    return new SubscriptionSuspensionDTO(
+                        firstOverdueInvoice.Created.AddDays(gracePeriod),
+                        firstOverdueInvoice.PeriodEnd,
+                        gracePeriod);
+                }
+            case "send_invoice":
+                {
+                    var firstOverdueInvoice = openInvoices
+                        .Where(invoice => invoice.DueDate < currentDate)
+                        .MinBy(invoice => invoice.Created);
+
+                    if (firstOverdueInvoice?.DueDate == null)
+                    {
+                        return null;
+                    }
+
+                    const int gracePeriod = 30;
+
+                    return new SubscriptionSuspensionDTO(
+                        firstOverdueInvoice.DueDate.Value.AddDays(gracePeriod),
+                        firstOverdueInvoice.PeriodEnd,
+                        gracePeriod);
+                }
+            default: return null;
+        }
+    }
 }