fix(backend): add unique index to auth methods

Foxnouns.Backend/Database/Migrations/20241128202508_AddAuthMethodUniqueIndex.cs

@@ -0,0 +1,47 @@
+using Microsoft.EntityFrameworkCore.Infrastructure;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Foxnouns.Backend.Database.Migrations
+{
+    /// <inheritdoc />
+    [DbContext(typeof(DatabaseContext))]
+    [Migration("20241128202508_AddAuthMethodUniqueIndex")]
+    public partial class AddAuthMethodUniqueIndex : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateIndex(
+                name: "ix_auth_methods_auth_type_remote_id",
+                table: "auth_methods",
+                columns: new[] { "auth_type", "remote_id" },
+                unique: true,
+                filter: "fediverse_application_id IS NULL"
+            );
+
+            migrationBuilder.CreateIndex(
+                name: "ix_auth_methods_auth_type_remote_id_fediverse_application_id",
+                table: "auth_methods",
+                columns: new[] { "auth_type", "remote_id", "fediverse_application_id" },
+                unique: true,
+                filter: "fediverse_application_id IS NOT NULL"
+            );
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "ix_auth_methods_auth_type_remote_id",
+                table: "auth_methods"
+            );
+
+            migrationBuilder.DropIndex(
+                name: "ix_auth_methods_auth_type_remote_id_fediverse_application_id",
+                table: "auth_methods"
+            );
+        }
+    }
+}