IndexAttribute 优化，提升代码实现可读性

[BI7PRK]

Feature 特性

namespace FreeSql.DataAnnotations;

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
public class IndexAttribute : Attribute
{
     public string Fields { get; set; }
}

简要描述原因

Fields 能否由string改为string[]

   public string[] Fields { get; set; }

  public IndexAttribute(string name, params string[] fields)
  {
      this.Name = name;
      this.Fields = fields;
  }

使用场景

[Index("{tablename}_user_phone", "user_id", "phone`)]

[2881099]

[Index("{tablename}_user_phone", $"{nameof(user_id)}, {nameof(phone)}")]

差不了太多