fix(Mautic Node): Fix authentication issue (#3761)

* Fixes mautic credential issue

* removed unused imports

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>

packages/nodes-base/credentials/MauticApi.credentials.ts

@@ -1,8 +1,7 @@
 import {
-	ICredentialDataDecryptedObject,
+	IAuthenticateGeneric,
 	ICredentialTestRequest,
 	ICredentialType,
-	IHttpRequestOptions,
 	INodeProperties,
 } from 'n8n-workflow';
 
@@ -34,22 +33,16 @@ export class MauticApi implements ICredentialType {
 			default: '',
 		},
 	];
-	async authenticate(
-		credentials: ICredentialDataDecryptedObject,
-		requestOptions: IHttpRequestOptions,
-	): Promise<IHttpRequestOptions> {
-		const { url, username, password } = credentials as {
-			url: string;
-			username: string;
-			password: string;
-		};
-		const credentialUrl = url.endsWith('/') ? `${url}api/users/self` : `${url}/api/users/self`;
-		const base64Key = Buffer.from(`${username}:${password}`).toString('base64');
-		requestOptions.headers!['Authorization'] = `Basic ${base64Key}`;
-		requestOptions.url = credentialUrl ? credentialUrl : requestOptions.url;
 
-		return requestOptions;
-	}
+	authenticate: IAuthenticateGeneric = {
+		type: 'generic',
+		properties: {
+			auth: {
+				username: '={{$credentials.username}}',
+				password: '={{$credentials.password}}',
+			},
+		},
+	};
 
 	test: ICredentialTestRequest = {
 		request: {