Expand Index struct to also get the original field name

This is needed in postgres, since we store data as jsonb so struct
fields can't get renamed

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

heromodels/src/models/biz/company.rs

@@ -84,6 +84,9 @@ impl Index for CompanyNameIndex {
     fn key() -> &'static str {
         "name"
     }
+    fn field_name() -> &'static str {
+        "name"
+    }
 }
 
 pub struct CompanyRegistrationNumberIndex;
@@ -93,6 +96,9 @@ impl Index for CompanyRegistrationNumberIndex {
     fn key() -> &'static str {
         "registration_number"
     }
+    fn field_name() -> &'static str {
+        "registration_number"
+    }
 }
 
 // --- Builder Pattern ---