return challenge tokens in send endpoint as explicit key

src/client/client.go

@@ -161,7 +161,8 @@ type SignalCliIdentityEntry struct {
 }
 
 type SendResponse struct {
-	Timestamp int64 `json:"timestamp"`
+	Timestamp       int64    `json:"timestamp"`
+	ChallengeTokens []string `json:"challenge_tokens"`
 }
 
 type About struct {
@@ -459,6 +460,15 @@ func (s *SignalClient) send(number string, message string,
 			if strings.Contains(err.Error(), signalCliV2GroupError) {
 				return nil, errors.New("Cannot send message to group - please first update your profile.")
 			}
+
+			switch errorType := err.(type) {
+			case *RateLimitErrorType:
+				rateLimitError := errors.New(err.Error() + ". Use the attached challenge tokens to lift the rate limit restrictions via the '/v1/accounts/{number}/rate-limit-challenge' endpoint.")
+				resp.ChallengeTokens = errorType.ChallengeTokens
+				return &resp, rateLimitError
+			default:
+				return nil, err
+			}
 			return nil, err
 		}
 	} else {

src/client/jsonrpc2.go

@@ -7,7 +7,6 @@ import (
 	"net"
 	"time"
 	"sync"
-	"strings"
 
 	"github.com/bbernhard/signal-cli-rest-api/utils"
 	uuid "github.com/gofrs/uuid"
@@ -45,6 +44,15 @@ type RateLimitResult struct {
 	Token string `json:"token"`
 }
 
+type RateLimitErrorType struct {
+	ChallengeTokens []string
+	Err             error
+}
+
+func (r *RateLimitErrorType) Error() string {
+	return r.Err.Error()
+}
+
 type JsonRpc2Client struct {
 	conn                     net.Conn
 	receivedResponsesById    map[string]chan JsonRpc2MessageResponse
@@ -151,7 +159,10 @@ func (r *JsonRpc2Client) getRaw(command string, account *string, args interface{
 				challengeTokens = append(challengeTokens, rateLimitResult.Token)
 			}
 
-			return "", errors.New(resp.Err.Message + " Challenge Tokens: " + strings.Join(challengeTokens, ","))
+			return "", &RateLimitErrorType{
+							ChallengeTokens: challengeTokens,
+							Err : errors.New(resp.Err.Message),
+						}
 		}
 		return "", errors.New(resp.Err.Message)
 	}