Is your feature request related to a problem? Please describe.
In Postgres server, I need to perform these steps in these exact order:

1. Call a function in "postgres" database (pgaadauth_create_principal())
2. Create schema objects in "my-application" database
3. Call a function in "postgres" (`cron.schedule_in_database(... , ... ,'my-application'))

Describe the solution you'd like
To be discussed, but:

1. Add some hooks, that will allow to run custom C# code before or after migration step, such as:

   void BeforeUp();
   

   This would allow me to write custom C# code that executes custom script in different database.

   public void BeforeUp()
   {
     using var connection = new NpgsqlConnection(postgresConnStr);
     connection.Open();
     using var jobCommand = connection.CreateCommand();
     jobCommand.CommandText = $"""
   	SELECT cron.schedule_in_database('{CleanupJobName}','0 1 * * 6', 'CALL "{AppSchema}"."DbCleanup"();', 		 
         """;
     jobCommand.ExecuteNonQuery();
   }
   

2. Allow connection string customization per migration
3. Allow to setup multiple Migrators each with its own set of migrations and connectionstring + create RunnerOrchestrator

Is this a feature you'd like to submit a PR for?
if we agree on API design...