Implement Max capacity logic on registration

src/EventHub.Domain.Shared/EventHubErrorCodes.cs

@@ -7,5 +7,6 @@
         public const string EventEndTimeCantBeEarlierThanStartTime = "EventHub:EventEndTimeCantBeEarlierThanStartTime";
         public const string CantRegisterOrUnregisterForAPastEvent = "EventHub:CantRegisterOrUnregisterForAPastEvent";
         public const string NotAuthorizedToUpdateOrganizationProfile = "EventHub:NotAuthorizedToUpdateOrganizationProfile";
+        public const string CapacityOfEventFull = "EventHub:CapacityOfEventFull";
     }
 }

src/EventHub.Domain.Shared/Localization/EventHub/en.json

@@ -47,6 +47,7 @@
     "EditOrganization": "Edit Organization",
     "PersonalWebsite": "Personal Website",
     "SocialMedia": "Social Media",
-    "EventHub:NotAuthorizedToUpdateOrganizationProfile": "You are not authorized to update the \"{OrganizationName}\" organization."
+    "EventHub:NotAuthorizedToUpdateOrganizationProfile": "You are not authorized to update the \"{OrganizationName}\" organization.",
+    "EventHub:CapacityOfEventFull": "\"{EventTitle}\" event capacity is full!"
   }
 }

src/EventHub.Domain/Events/Registrations/EventRegistrationManager.cs

@@ -27,7 +27,15 @@ namespace EventHub.Events.Registrations
             {
                 return;
             }
+            
+            var registrationCount = await _eventRegistrationRepository.CountAsync(x => x.EventId == @event.Id);
 
+            if (@event.Capacity != null &&  registrationCount >= @event.Capacity)
+            {
+                throw new BusinessException(EventHubErrorCodes.CapacityOfEventFull)
+                    .WithData("EventTitle", @event.Title);
+            }
+                
             await _eventRegistrationRepository.InsertAsync(
                 new EventRegistration(
                     GuidGenerator.Create(),