[PM-12601] Add discount to MSP during creation in Admin Portal (#5391)

* Add Provider DiscountId to database and Stripe customer

* Fix tests

* Add missing EF migrations

* Run dotnet format

util/MySqlMigrations/Migrations/20250213140357_AddColumn_ProviderDiscountId.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace Bit.MySqlMigrations.Migrations;
+
+/// <inheritdoc />
+public partial class AddColumn_ProviderDiscountId : Migration
+{
+    /// <inheritdoc />
+    protected override void Up(MigrationBuilder migrationBuilder)
+    {
+        migrationBuilder.AddColumn<string>(
+            name: "DiscountId",
+            table: "Provider",
+            type: "longtext",
+            nullable: true)
+            .Annotation("MySql:CharSet", "utf8mb4");
+    }
+
+    /// <inheritdoc />
+    protected override void Down(MigrationBuilder migrationBuilder)
+    {
+        migrationBuilder.DropColumn(
+            name: "DiscountId",
+            table: "Provider");
+    }
+}