REST bank transfers fail due to encoding. (#6536)

Bank module REST endpoint bank/accounts/{addr}/transfers
was returning invalid StdTx format.

types/rest/rest.go

@@ -3,6 +3,7 @@
 package rest
 
 import (
+	"bytes"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -442,3 +443,23 @@ func GetRequest(url string) ([]byte, error) {
 
 	return body, nil
 }
+
+// PostRequest defines a wrapper around an HTTP POST request with a provided URL and data.
+// An error is returned if the request or reading the body fails.
+func PostRequest(url string, contentType string, data []byte) ([]byte, error) {
+	res, err := http.Post(url, contentType, bytes.NewBuffer(data)) // nolint:gosec
+	if err != nil {
+		return nil, fmt.Errorf("error while sending post request: %w", err)
+	}
+
+	bz, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		return nil, fmt.Errorf("error reading response body: %w", err)
+	}
+
+	if err = res.Body.Close(); err != nil {
+		return nil, err
+	}
+
+	return bz, nil
+}