Update macro to use #[index] attributes

- Also use proper types for index.
 - Update DB interface to be more flexible for index params

Signed-off-by: Lee Smet <lee.smet@hotmail.com>

heromodels/examples/model_macro_example.rs

@@ -8,7 +8,7 @@ use serde::{Serialize, Deserialize};
 pub struct SimpleUser {
     pub base_data: BaseModelData,
     
-    /// @index
+    #[index]
     pub login: String,
     
     pub full_name: String,
@@ -20,10 +20,10 @@ pub struct SimpleUser {
 pub struct CustomUser {
     pub base_data: BaseModelData,
     
-    /// @index(name = "user_name", key_type = "str")
+    #[index(name = "user_name")]
     pub login_name: String,
     
-    /// @index(key_type = "bool")
+    #[index]
     pub is_active: bool,
     
     pub full_name: String,