Added toJSON method to Connection class (#849)

* Added toJSON method to Connection class

* Updated test

* Updated typings

lib/Connection.d.ts

@@ -78,6 +78,7 @@ export default class Connection {
   buildRequestObject(params: any): http.ClientRequestArgs;
   // @ts-ignore
   [inspect.custom](object: any, options: InspectOptions): string;
+  toJSON(): any;
 }
 
 export {};

lib/Connection.js

@@ -239,6 +239,19 @@ class Connection {
       roles: this.roles
     }
   }
+
+  toJSON () {
+    return {
+      url: this.url,
+      id: this.id,
+      headers: this.headers,
+      deadCount: this.deadCount,
+      resurrectTimeout: this.resurrectTimeout,
+      _openRequests: this._openRequests,
+      status: this.status,
+      roles: this.roles
+    }
+  }
 }
 
 Connection.statuses = {

test/unit/connection.test.js

@@ -794,3 +794,16 @@ test('Port handling', t => {
 
   t.end()
 })
+
+test('Should not add agent and ssl to the serialized connection', t => {
+  const connection = new Connection({
+    url: new URL('http://localhost:9200')
+  })
+
+  t.strictEqual(
+    JSON.stringify(connection),
+    '{"url":"http://localhost:9200/","id":"http://localhost:9200/","headers":null,"deadCount":0,"resurrectTimeout":0,"_openRequests":0,"status":"alive","roles":{"master":true,"data":true,"ingest":true,"ml":false}}'
+  )
+
+  t.end()
+})