Rest Api Call Node fixes: throws null data for next node in message, added default header Content-Type

rule-engine/rule-engine-components/src/main/java/org/thingsboard/rule/engine/rest/TbHttpClient.java

@@ -207,7 +207,8 @@ public class TbHttpClient {
         metaData.putValue(STATUS_CODE, response.getStatusCode().value() + "");
         metaData.putValue(STATUS_REASON, response.getStatusCode().getReasonPhrase());
         response.getHeaders().toSingleValueMap().forEach(metaData::putValue);
-        return ctx.transformMsg(origMsg, origMsg.getType(), origMsg.getOriginator(), metaData, response.getBody());
+        String body = response.getBody() == null ? "{}" : response.getBody();
+        return ctx.transformMsg(origMsg, origMsg.getType(), origMsg.getOriginator(), metaData, body);
     }
 
     private TbMsg processFailureResponse(TbContext ctx, TbMsg origMsg, ResponseEntity<String> response) {

rule-engine/rule-engine-components/src/main/java/org/thingsboard/rule/engine/rest/TbRestApiCallNodeConfiguration.java

@@ -17,6 +17,8 @@ package org.thingsboard.rule.engine.rest;
 
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import lombok.Data;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.MediaType;
 import org.thingsboard.rule.engine.api.NodeConfiguration;
 import org.thingsboard.rule.engine.credentials.AnonymousCredentials;
 import org.thingsboard.rule.engine.credentials.ClientCredentials;
@@ -51,7 +53,7 @@ public class TbRestApiCallNodeConfiguration implements NodeConfiguration<TbRestA
         TbRestApiCallNodeConfiguration configuration = new TbRestApiCallNodeConfiguration();
         configuration.setRestEndpointUrlPattern("http://localhost/api");
         configuration.setRequestMethod("POST");
-        configuration.setHeaders(Collections.emptyMap());
+        configuration.setHeaders(Collections.singletonMap(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE));
         configuration.setUseSimpleClientHttpFactory(false);
         configuration.setReadTimeoutMs(0);
         configuration.setMaxParallelRequestsCount(0);