Log successful submit as such

src/mining.cpp

@@ -197,6 +197,7 @@ void runStratumWorker(void *name) {
           case MINING_SET_DIFFICULTY: parse_mining_set_difficulty(line, currentPoolDifficulty);
                                       mMiner.poolDifficulty = currentPoolDifficulty;
                                       break;
+          case STRATUM_SUCCESS:       Serial.println("  Parsed JSON: Success"); break;
           default:                    Serial.println("  Parsed JSON: unknown"); break;
 
       }

src/stratum.cpp

@@ -142,8 +142,13 @@ stratum_method parse_mining_method(String line)
 
     if (error || checkError(doc)) return STRATUM_PARSE_ERROR;
 
-    if (!doc.containsKey("method")) return STRATUM_UNKNOWN;
-    
+    if (!doc.containsKey("method")) {
+      // "error":null means success
+      if (doc["error"].isNull())
+        return STRATUM_SUCCESS;
+      else
+        return STRATUM_UNKNOWN;
+    }
     stratum_method result = STRATUM_UNKNOWN;
 
     if (strcmp("mining.notify", (const char*) doc["method"]) == 0) {

src/stratum.h

@@ -38,6 +38,7 @@ typedef struct {
 } mining_job;
 
 typedef enum {
+    STRATUM_SUCCESS,
     STRATUM_UNKNOWN,
     STRATUM_PARSE_ERROR,
     MINING_NOTIFY,