public IEnumerable <PostEntity> GetTagPostsAsync(string tag)
{
var postIds = _postTagService.GetPostsWithParticularTag(tag).ToList();
var posts = _postRepository
.Where(p => postIds.Contains(p.Id))
.OrderByDescending(c => c.CreatedAt);
return(posts.Select(p => _mapper.Map <PostEntity>(p)));
}