message: fix convert failed error
diff: use std::collections::HashMap;
  -
  +use serde_json::Value;
  use spotify::spotify_enum::TYPE;
  use super::image::Image;
  #[derive(Clone, Debug, Serialize, Deserialize)]
  @@ -14,10 +14,11 @@ pub struct Artist {
  pub uri: String,
  }
  +
  #[derive(Clone, Debug,Serialize, Deserialize)]
  pub struct ArtistDetailed {
  pub external_urls: HashMap<String, String>,
  - pub followers: HashMap<String, String>,
  + pub followers: HashMap<String, Option<Value>>,
  pub genres: Vec<String>,
  pub href: String,
  pub id: String,
  