refactor: remove utils pkg

BREAKING CHANGE: utils package has been removed in favor of specific new
packages (http, crypto, strings)

pkg/crypto/sign.go

@@ -0,0 +1,27 @@
+package crypto
+
+import (
+	"encoding/json"
+	"errors"
+
+	"gopkg.in/square/go-jose.v2"
+)
+
+func Sign(object interface{}, signer jose.Signer) (string, error) {
+	payload, err := json.Marshal(object)
+	if err != nil {
+		return "", err
+	}
+	return SignPayload(payload, signer)
+}
+
+func SignPayload(payload []byte, signer jose.Signer) (string, error) {
+	if signer == nil {
+		return "", errors.New("missing signer")
+	}
+	result, err := signer.Sign(payload)
+	if err != nil {
+		return "", err
+	}
+	return result.CompactSerialize()
+}