Add Faucet endpoint (#36)

* Add internal methods for faucet feature

* Add grpc handler

* Lint

asp/internal/interface/grpc/handlers/utils.go

@@ -0,0 +1,33 @@
+package handlers
+
+import (
+	"encoding/hex"
+	"fmt"
+
+	"github.com/ark-network/ark/common"
+	"github.com/vulpemventures/go-elements/psetv2"
+)
+
+func parseTxs(txs []string) ([]string, error) {
+	if len(txs) <= 0 {
+		return nil, fmt.Errorf("missing list of forfeit txs")
+	}
+	for _, tx := range txs {
+		if _, err := psetv2.NewPsetFromBase64(tx); err != nil {
+			return nil, fmt.Errorf("invalid tx format")
+		}
+	}
+	return txs, nil
+}
+
+func parseAddress(addr string) (string, error) {
+	if len(addr) <= 0 {
+		return "", fmt.Errorf("missing address")
+	}
+	_, userPubkey, _, err := common.DecodeAddress(addr)
+	if err != nil {
+		return "", fmt.Errorf("invalid address: %s", err)
+	}
+	pubkey := hex.EncodeToString(userPubkey.SerializeCompressed())
+	return pubkey, nil
+}