I use a TFS 2015 instance (it will be soon decommissioned). In a release definition I need to use some sensitive data (credentials). As of now I tried setting the secrets as in this guide but this is a feature supported only from TFS 2018 on. In fact, in TFS 2015 I cannot see the "Environment variables" section that is needed to decrypt the "locked" configurations.
What are the possible options here to have a per-project set of encrypted sensitive data that I can then retrieve and use in the release scripts? Is there any credential manager (like the one in Jenkins) in TFS 2015?