Enhance documentation for API client and vehicle structures; improve test function naming for clarity

mysubaru.go

@@ -4,7 +4,7 @@ import (
 	"encoding/json"
 )
 
-// Response .
+// Response represents the structure of a response from the MySubaru API.
 type Response struct {
 	Success   bool            `json:"success"`             // true | false
 	ErrorCode string          `json:"errorCode,omitempty"` // string | Error message if Success is false
@@ -25,7 +25,7 @@ type Response struct {
 // Unmarshal .
 // func (r *Response) Unmarshal(b []byte) {}
 
-// Request .
+// Request represents the structure of a request to the MySubaru API.
 type Request struct {
 	Vin                       string  `json:"vin"`                                 //
 	Pin                       string  `json:"pin"`                                 //