changing error log structure

lib/cartodb/middleware/error-middleware.js

@@ -167,12 +167,14 @@ function logErrors(errors, statusCode, res) {
     const mainError = errorsCopy.shift();
 
     let errorsLog = {
-        statusCode: statusCode || 200,
-        message:    mainError.message,
-        name:       mainError.name,
-        label:      mainError.label,
-        type:       mainError.type,
-        subtype:    mainError.subtype
+        mainError: {
+            statusCode: statusCode || 200,
+            message:    mainError.message,
+            name:       mainError.name,
+            label:      mainError.label,
+            type:       mainError.type,
+            subtype:    mainError.subtype
+        }
     };
 
     errorsLog.moreErrors = errorsCopy.map(error => {

test/unit/cartodb/base_controller.js

@@ -44,12 +44,14 @@ describe('error-middleware', function() {
         };
 
         const errorHeader = {
-            statusCode: 400,
-            message: error.message,
-            name: error.name,
-            label: error.label,
-            type: error.type,
-            subtype: error.subtype,
+            mainError: {
+                statusCode: 400,
+                message: error.message,
+                name: error.name,
+                label: error.label,
+                type: error.type,
+                subtype: error.subtype,
+            },
             moreErrors: [{
                 message: error.message,
                 name: error.name,
@@ -94,12 +96,14 @@ describe('error-middleware', function() {
         };
 
         const errorHeader = {
-            statusCode: 400,
-            message: error.message,
-            name: error.name,
-            label: error.label,
-            type: error.type,
-            subtype: error.subtype,
+            mainError: {
+                statusCode: 400,
+                message: error.message,
+                name: error.name,
+                label: error.label,
+                type: error.type,
+                subtype: error.subtype,
+            },
             moreErrors: [{
                 message: error.message,
                 name: error.name,