Fixed the erroneous usage of aggregate id members because it was not using the "official" mapping. Closes GH-3851

Author: jeremydmiller

src/EventSourcingTests/Bugs/Bug_3851_should_use_document_mapping_from_store_options_for_id_member.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Threading.Tasks;
+using Marten.Testing.Harness;
+using Shouldly;
+using Xunit;
+
+namespace EventSourcingTests.Bugs;
+
+public class Bug_3851_should_use_document_mapping_from_store_options_for_id_member : BugIntegrationContext
+{
+    [Fact]
+    public async Task aggregate_correctly()
+    {
+        StoreOptions(opts =>
+        {
+            opts.Schema.For<EntityWithoutConventionalId>().Identity(x => x.OtherId);
+
+        });
+
+        var streamId = Guid.NewGuid();
+
+        theSession.Events.StartStream<EntityWithoutConventionalId>(streamId, new EntityCreated("one"),
+            new ContentAdded("two"));
+
+        await theSession.SaveChangesAsync();
+
+        var entity = await theSession.Events.AggregateStreamAsync<EntityWithoutConventionalId>(streamId);
+
+        entity.InitialContent.ShouldBe("one");
+        entity.MoreContent.ShouldBe("two");
+    }
+}
+
+public class EntityWithoutConventionalId
+{
+    public Guid OtherId { get; set; }
+    public string? InitialContent { get; set; }
+    public string? MoreContent { get; set; }
+
+    public void Apply(EntityCreated @event)
+    {
+        InitialContent = @event.Content;
+    }
+
+    public void Apply(ContentAdded @event)
+    {
+        MoreContent = @event.Content;
+    }
+}
+
+public record EntityCreated(string Content);
+public record ContentAdded(string Content);

src/Marten/Events/EventGraph.cs

@@ -87,7 +87,7 @@ internal EventGraph(StoreOptions options)
 
     public IAggregatorSource<IQuerySession>? Build<TDoc>()
     {
-        var idType = new DocumentMapping(typeof(TDoc), Options).IdType;
+        var idType = Options.Storage.MappingFor(typeof(TDoc)).IdType;
         return typeof(SingleStreamProjection<,>)
             .CloseAndBuildAs<IAggregatorSource<IQuerySession>>(typeof(TDoc), idType);
     }