I created a packageMigrationbase class, this adds a yesno property to an existing doctype

```csharp
public class PublishRootBranchPostMigration : MigrationBase
{
        private readonly ILogger<PublishRootBranchPostMigration> _logger;
        private readonly IDataTypeService _dataTypeService;
        private readonly IContentTypeService _contentTypeService;

        public PublishRootBranchPostMigration(
            ILogger<PublishRootBranchPostMigration> logger,
            IMigrationContext context,
            IDataTypeService dataTypeService,
            IContentTypeService contentTypeService) : base(context)
        {
            _logger = logger;
            _dataTypeService = dataTypeService;
            _contentTypeService = contentTypeService;
        }
        protected override void Migrate(){
          AddAnswerProperty();
        }
        private void AddAnswerProperty()
        {
            try
            {
                var dataTypeDefinitions = _dataTypeService.GetAll().ToArray(); 
                var truefalse = dataTypeDefinitions.FirstOrDefault(p => p.EditorAlias.ToLower() == "umbraco.truefalse" && p.Name.Contains("Resolved")); //we want the TrueFalse data type.
                
                var forumPost = _contentTypeService.Get("forumPost");
                var chack = forumPost.PropertyGroups;
                if (forumPost != null && truefalse != null)
                {
                    if (!forumPost.PropertyTypes.Any(p => p.Alias == "answer"))
                    {
                        var answerPropertyType = new PropertyType(_shortStringHelper, truefalse)
                        {
                            Name = "Answer",
                            Alias = "answer",
                            Description = "Marked as solution/resolved.",
                        };
                        forumPost.AddPropertyType(answerPropertyType,"general");
                        _contentTypeService.Save(forumPost);
                    }
                }
            }
            catch (Exception e)
            {
                _logger.LogError(e,"Adding Ansered property");
                throw;
            }
        }
}