Add UsePostgres overload for data source configuration

src/Trax.Effect.Data.Postgres/Extensions/ModelBuilderExtensions.cs

@@ -67,7 +67,20 @@ public static ModelBuilder AddPostgresEnums(this ModelBuilder modelBuilder)
     /// This method is typically called when setting up the DbContextFactory in the
     /// AddPostgresEffect extension method.
     /// </remarks>
-    public static NpgsqlDataSource BuildDataSource(string connectionString)
+    public static NpgsqlDataSource BuildDataSource(string connectionString) =>
+        BuildDataSource(connectionString, configure: null);
+
+    /// <summary>
+    /// Builds a PostgreSQL data source with enum mappings and optional custom configuration.
+    /// </summary>
+    /// <param name="connectionString">The connection string to use</param>
+    /// <param name="configure">Optional action to configure the data source builder after enum mappings
+    /// (e.g., set <c>ConnectionStringBuilder.MaxPoolSize</c> or enable multiplexing)</param>
+    /// <returns>A configured NpgsqlDataSource</returns>
+    public static NpgsqlDataSource BuildDataSource(
+        string connectionString,
+        Action<NpgsqlDataSourceBuilder>? configure
+    )
     {
         var npgsqlDataSourceBuilder = new NpgsqlDataSourceBuilder(connectionString);
 
@@ -78,6 +91,8 @@ public static NpgsqlDataSource BuildDataSource(string connectionString)
         npgsqlDataSourceBuilder.MapEnum<WorkQueueStatus>("trax.work_queue_status");
         npgsqlDataSourceBuilder.MapEnum<MisfirePolicy>("trax.misfire_policy");
 
+        configure?.Invoke(npgsqlDataSourceBuilder);
+
         return npgsqlDataSourceBuilder.Build();
     }
 

src/Trax.Effect.Data.Postgres/Extensions/ServiceExtensions.cs

@@ -87,14 +87,36 @@ public static TraxEffectBuilder SkipMigrations(this TraxEffectBuilder builder)
     public static TraxEffectBuilderWithData UsePostgres(
         this TraxEffectBuilder configurationBuilder,
         string connectionString
+    ) => configurationBuilder.UsePostgres(connectionString, configureDataSource: null);
+
+    /// <summary>
+    /// Adds PostgreSQL database support to the Trax.Effect system with custom data source configuration.
+    /// </summary>
+    /// <param name="configurationBuilder">The Trax.Core effect configuration builder</param>
+    /// <param name="connectionString">The connection string to the PostgreSQL database</param>
+    /// <param name="configureDataSource">Optional action to configure the <see cref="NpgsqlDataSourceBuilder"/>
+    /// after enum mappings. Use this to tune connection pool settings, enable multiplexing, or add custom type mappings.
+    /// <code>
+    /// effects.UsePostgres(connectionString, dataSource =>
+    ///     dataSource.ConnectionStringBuilder.MaxPoolSize = 50);
+    /// </code>
+    /// </param>
+    /// <returns>The configuration builder for method chaining</returns>
+    public static TraxEffectBuilderWithData UsePostgres(
+        this TraxEffectBuilder configurationBuilder,
+        string connectionString,
+        Action<NpgsqlDataSourceBuilder>? configureDataSource
     )
     {
         // Migrate the database schema to the latest version (unless explicitly skipped)
         if (!configurationBuilder.MigrationsDisabled)
             DatabaseMigrator.Migrate(connectionString).Wait();
 
         // Create a data source with enum mappings and register for disposal on shutdown
-        var dataSource = ModelBuilderExtensions.BuildDataSource(connectionString);
+        var dataSource = ModelBuilderExtensions.BuildDataSource(
+            connectionString,
+            configureDataSource
+        );
         configurationBuilder.ServiceCollection.AddSingleton(dataSource);
 
         // Register the DbContextFactory

tests/Trax.Effect.Tests.Integration/UnitTests/Configuration/SkipMigrationsTests.cs

@@ -137,4 +137,66 @@ public void UsePostgres_WithSkipMigrations_StillRegistersDataContext()
     }
 
     #endregion
+
+    #region UsePostgres with ConfigureDataSource
+
+    [Test]
+    public void UsePostgres_WithConfigureAction_DoesNotThrow()
+    {
+        var act = () =>
+            new ServiceCollection().AddTrax(trax =>
+                trax.AddEffects(effects =>
+                    effects
+                        .SkipMigrations()
+                        .UsePostgres(
+                            UnreachableConnectionString,
+                            dataSource => dataSource.ConnectionStringBuilder.MaxPoolSize = 50
+                        )
+                )
+            );
+
+        act.Should().NotThrow();
+    }
+
+    [Test]
+    public void UsePostgres_WithConfigureAction_StillRegistersDbContextFactory()
+    {
+        var services = new ServiceCollection();
+
+        services.AddTrax(trax =>
+            trax.AddEffects(effects =>
+                effects
+                    .SkipMigrations()
+                    .UsePostgres(
+                        UnreachableConnectionString,
+                        dataSource => dataSource.ConnectionStringBuilder.MaxPoolSize = 50
+                    )
+            )
+        );
+
+        services
+            .Should()
+            .Contain(sd =>
+                sd.ServiceType.IsGenericType
+                && sd.ServiceType.GetGenericTypeDefinition()
+                    == typeof(Microsoft.EntityFrameworkCore.IDbContextFactory<>)
+            );
+    }
+
+    [Test]
+    public void UsePostgres_WithNullConfigureAction_BehavesLikeDefault()
+    {
+        var act = () =>
+            new ServiceCollection().AddTrax(trax =>
+                trax.AddEffects(effects =>
+                    effects
+                        .SkipMigrations()
+                        .UsePostgres(UnreachableConnectionString, configureDataSource: null)
+                )
+            );
+
+        act.Should().NotThrow();
+    }
+
+    #endregion
 }