[PM-12420] Stripe events recovery (#4793)

* Billing: Add event recovery endpoints

* Core: Add InternalBilling to BaseServiceUriSettings

* Admin: Scaffold billing section

* Admin: Scaffold ProcessStripeEvents section

* Admin: Implement event processing

* Run dotnet format

src/Admin/Billing/Models/ProcessStripeEvents/EventsFormModel.cs

@@ -0,0 +1,29 @@
+using System.ComponentModel;
+using System.ComponentModel.DataAnnotations;
+
+namespace Bit.Admin.Billing.Models.ProcessStripeEvents;
+
+public class EventsFormModel : IValidatableObject
+{
+    [Required]
+    public string EventIds { get; set; }
+
+    [Required]
+    [DisplayName("Inspect Only")]
+    public bool Inspect { get; set; }
+
+    public List<string> GetEventIds() =>
+        EventIds?.Split([Environment.NewLine], StringSplitOptions.RemoveEmptyEntries)
+            .Select(eventId => eventId.Trim())
+            .ToList() ?? [];
+
+    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
+    {
+        var eventIds = GetEventIds();
+
+        if (eventIds.Any(eventId => !eventId.StartsWith("evt_")))
+        {
+            yield return new ValidationResult("Event Ids must start with 'evt_'.");
+        }
+    }
+}