fix: offload building DTOs to GUHF

DTO building allows for fully returning correct event's
skills and registrations

WebApp/Endpoints/GeneralUseHelperFunctions.cs

@@ -1,5 +1,6 @@
-using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore;
 using WebApp.Data;
+using WebApp.DTOs;
 using WebApp.Entities;
 
 namespace WebApp.Endpoints;
@@ -112,4 +113,49 @@ public class GeneralUseHelpers
         // Sprawdza, czy któreś ze słów pasuje (nawet częściowo) do searchTerm
         return words.Any(word => word.Contains(searchTerm, StringComparison.OrdinalIgnoreCase));
     }
+
+    public async Task<List<EventDetailsDto>> BuildDetailedEventsDto(ApplicationDbContext context, bool includeEventRegistrations = false)
+    {
+        // https://khalidabuhakmeh.com/ef-core-and-aspnet-core-cycle-issue-and-solution
+
+        // Jeśli token należy do organizacji, która utworzyła to wydarzenie,
+        // to zwróć także EventRegistrations. W przeciwnym razie niech będzie to
+        // puste pole.
+        ICollection<EventRegistrationDto> ERs = new List<EventRegistrationDto>();
+        if (includeEventRegistrations)
+        {
+            ERs = await context
+                .EventRegistrations
+                .Select(er => new EventRegistrationDto
+                {
+                    EventId = er.EventId,
+                    UserId = er.UserId,
+                    UserName = er.User.FirstName + " " + er.User.LastName,
+                    RegisteredAt = er.RegisteredAt
+                }).ToListAsync();
+        }
+
+        List<EventDetailsDto> result = await context
+                .Events
+                .Select(e => new EventDetailsDto
+                {
+                    EventId = e.EventId,
+                    OrganisationId = e.OrganisationId,
+                    OrganisationName = e.Organisation.Name,
+                    Title = e.Title,
+                    Description = e.Description,
+                    Location = e.Location,
+                    EventDate = e.EventDate,
+                    EventSkills = e
+                        .EventSkills
+                        .Select(es => new SkillSummaryDto
+                        {
+                            SkillId = es.SkillId,
+                            SkillName = es.Skill.Name
+                        }).ToList(),
+                    EventRegistrations = ERs
+                }).ToListAsync();
+
+        return result;
+    }
 }