added get merch prices method

internal/api/merch/dto.go

@@ -1,5 +1,7 @@
 package merch
 
+import "time"
+
 type merchBundle struct {
 	Merch     *Merch
 	Surugaya  *Surugaya
@@ -30,3 +32,19 @@ type ListResponse struct {
 	MerchUuid string `json:"merch_uuid"`
 	Name      string `json:"name"`
 }
+
+type PriceEntry struct {
+	CreatedAt time.Time `json:"created_at"`
+	Value     int       `json:"value"`
+}
+
+type OriginWithPrices struct {
+	Origin Origin `json:"origin"`
+	Prices []PriceEntry
+}
+
+type PricesResponse struct {
+	Name      string             `json:"name"`
+	MerchUuid string             `json:"merch_uuid"`
+	Origins   []OriginWithPrices `json:"origins"`
+}