Removing string json's parameter from Runtime variable inside Movie's struct. Creating errors.go handling different json's error for our API.

internal/data/movies.go

@@ -15,7 +15,7 @@ type Movie struct {
 	/*
 		Use the Runtime type instead of int32. Note that the omitempty directive will still work on this: if the Runtime field has the underlying value 0, then it will be considered empty and omitted -- and the MarshalJSON() method we just made won't be called at all.
 	*/
-	Runtime Runtime  `json:"runtime,omitempty,string"`
+	Runtime Runtime  `json:"runtime,omitempty"`
 	Genres  []string `json:"genres,omitempty"`
 	Version int32    `json:"version"`
 }