[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/PostgresMigrations/Migrations/DatabaseContextModelSnapshot.cs

@@ -287,6 +287,9 @@ namespace Bit.PostgresMigrations.Migrations
                     b.Property<DateTime>("CreationDate")
                         .HasColumnType("timestamp with time zone");
 
+                    b.Property<string>("DiscountId")
+                        .HasColumnType("text");
+
                     b.Property<bool>("Enabled")
                         .HasColumnType("boolean");