Mailchimp OAuth2 support

packages/nodes-base/nodes/Mailchimp/Mailchimp.node.ts

@@ -69,9 +69,44 @@ export class Mailchimp implements INodeType {
 			{
 				name: 'mailchimpApi',
 				required: true,
-			}
+				displayOptions: {
+					show: {
+						authentication: [
+							'accessToken',
+						],
+					},
+				},
+			},
+			{
+				name: 'mailchimpOAuth2Api',
+				required: true,
+				displayOptions: {
+					show: {
+						authentication: [
+							'oAuth2',
+						],
+					},
+				},
+			},
 		],
 		properties: [
+			{
+				displayName: 'Authentication',
+				name: 'authentication',
+				type: 'options',
+				options: [
+					{
+						name: 'Access Token',
+						value: 'accessToken',
+					},
+					{
+						name: 'OAuth2',
+						value: 'oAuth2',
+					},
+				],
+				default: 'accessToken',
+				description: 'Method of authentication.',
+			},
 			{
 				displayName: 'Resource',
 				name: 'resource',
@@ -1536,6 +1571,7 @@ export class Mailchimp implements INodeType {
 					responseData = { success: true };
 				}
 			}
+			
 			if (Array.isArray(responseData)) {
 				returnData.push.apply(returnData, responseData as IDataObject[]);
 			} else {