feat(Mautic Node): Add credential test and allow trailing slash in host (#3080)

* Updated Mautic to stop trailing slashes from causing an issue

* Fixed oauth failing when there is a trailing slash in the mautic host

* Added credential test

packages/nodes-base/credentials/MauticOAuth2Api.credentials.ts

@@ -22,14 +22,14 @@ export class MauticOAuth2Api implements ICredentialType {
 			displayName: 'Authorization URL',
 			name: 'authUrl',
 			type: 'hidden',
-			default: '={{$self["url"]}}/oauth/v2/authorize',
+			default: '={{$self["url"].endsWith("/") ? $self["url"].slice(0, -1) : $self["url"]}}/oauth/v2/authorize',
 			required: true,
 		},
 		{
 			displayName: 'Access Token URL',
 			name: 'accessTokenUrl',
 			type: 'hidden',
-			default: '={{$self["url"]}}/oauth/v2/token',
+			default: '={{$self["url"].endsWith("/") ? $self["url"].slice(0, -1) : $self["url"]}}/oauth/v2/token',
 			required: true,
 		},
 		{