make `ToVikingId` nullable for system messages

src/Migrations/20250306194521_Messaging_ToVikingIdNullable.cs

@@ -0,0 +1,59 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace sodoff.Migrations
+{
+    /// <inheritdoc />
+    public partial class Messaging_ToVikingIdNullable : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Messages_Vikings_ToVikingId",
+                table: "Messages");
+
+            migrationBuilder.AlterColumn<int>(
+                name: "ToVikingId",
+                table: "Messages",
+                type: "INTEGER",
+                nullable: true,
+                oldClrType: typeof(int),
+                oldType: "INTEGER");
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Messages_Vikings_ToVikingId",
+                table: "Messages",
+                column: "ToVikingId",
+                principalTable: "Vikings",
+                principalColumn: "Id");
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropForeignKey(
+                name: "FK_Messages_Vikings_ToVikingId",
+                table: "Messages");
+
+            migrationBuilder.AlterColumn<int>(
+                name: "ToVikingId",
+                table: "Messages",
+                type: "INTEGER",
+                nullable: false,
+                defaultValue: 0,
+                oldClrType: typeof(int),
+                oldType: "INTEGER",
+                oldNullable: true);
+
+            migrationBuilder.AddForeignKey(
+                name: "FK_Messages_Vikings_ToVikingId",
+                table: "Messages",
+                column: "ToVikingId",
+                principalTable: "Vikings",
+                principalColumn: "Id",
+                onDelete: ReferentialAction.Cascade);
+        }
+    }
+}

src/Migrations/DBContextModelSnapshot.cs

@@ -343,7 +343,7 @@ namespace sodoff.Migrations
                     b.Property<int>("QueueID")
                         .HasColumnType("INTEGER");
 
-                    b.Property<int>("ToVikingId")
+                    b.Property<int?>("ToVikingId")
                         .HasColumnType("INTEGER");
 
                     b.Property<int>("VikingId")
@@ -982,9 +982,7 @@ namespace sodoff.Migrations
 
                     b.HasOne("sodoff.Model.Viking", "ToViking")
                         .WithMany("MessageBoard")
-                        .HasForeignKey("ToVikingId")
+                        .HasForeignKey("ToVikingId");
-                        .OnDelete(DeleteBehavior.Cascade)
-                        .IsRequired();
 
                     b.HasOne("sodoff.Model.Viking", "Viking")
                         .WithMany("MessagesMade")

src/Model/Message.cs

@@ -10,7 +10,7 @@ public class Message
     public int Id { get; set; }
 
     public int VikingId { get; set; }
-    public int ToVikingId { get; set; }
+    public int? ToVikingId { get; set; }
 
     public int QueueID { get; set; }
     public int? ConversationID { get; set; }