Adding validation for Rate extension definitions

tax/regime.go

@@ -473,9 +473,9 @@ func ValidateStructWithRegime(ctx context.Context, obj interface{}, fields ...*v
 	return ValidateInRegime(ctx, obj)
 }
 
-// Validate ensures the Category's contents are correct.
-func (c *Category) Validate() error {
-	err := validation.ValidateStruct(c,
+// ValidateWithContext ensures the Category's contents are correct.
+func (c *Category) ValidateWithContext(ctx context.Context) error {
+	err := validation.ValidateStructWithContext(ctx, c,
 		validation.Field(&c.Code, validation.Required),
 		validation.Field(&c.Name, validation.Required),
 		validation.Field(&c.Title, validation.Required),
@@ -507,17 +507,20 @@ func (s *Source) Validate() error {
 	)
 }
 
-// Validate checks that our tax definition is valid. This is only really
+// ValidateWithContext checks that our tax definition is valid. This is only really
 // meant to be used when testing new regional tax definitions.
-func (r *Rate) Validate() error {
-	err := validation.ValidateStruct(r,
+func (r *Rate) ValidateWithContext(ctx context.Context) error {
+	reg := ctx.Value(KeyRegime).(*Regime)
+	err := validation.ValidateStructWithContext(ctx, r,
 		validation.Field(&r.Key, validation.Required),
 		validation.Field(&r.Name, validation.Required),
 		validation.Field(&r.Values,
 			validation.When(r.Exempt, validation.Nil),
 			validation.By(checkRateValuesOrder),
 		),
-		validation.Field(&r.Extensions),
+		validation.Field(&r.Extensions,
+			validation.Each(InKeyDefs(reg.Extensions)),
+		),
 		validation.Field(&r.Map),
 		validation.Field(&r.Meta),
 	)

tax/scenario.go

@@ -117,7 +117,8 @@ func (s *Scenario) hasTags(docTags []cbc.Key) bool {
 	return false
 }
 
-// Validate checks the scenario for errors.
+// ValidateWithContext checks the scenario for errors, using the regime in the context
+// to validate the list of tags.
 func (s *Scenario) ValidateWithContext(ctx context.Context) error {
 	r := ctx.Value(KeyRegime).(*Regime)
 	err := validation.ValidateStructWithContext(ctx, s,