Get password & email address of the admin while creating a new tenant

Instead of;

````csharp
await DataSeeder.SeedAsync(tenant.Id);
````

It is possible to pass pass and email:

````csharp
await DataSeeder.SeedAsync(
    new DataSeedContext(tenant.Id)
        .WithProperty("AdminEmail", "admin@mytenant.com")
        .WithProperty("AdminPassword", "123456")
);
````

Get these from UI and pass to the seeder.