Feature allow custom root certificate authorities (CA)

**Is your feature request related to a problem? Please describe.**

The federation agent checks the HTTPS connection and only knows the root ca contained in the container / os. For use outside the public space, it is good to be able to announce your own root CAs

**Describe the solution you'd like**

Allow integration of own certificate collections. [Example](https://forfuncsake.github.io/post/2017/08/trust-extra-ca-cert-in-go-app/#and-the-winner-is).
One possibility is to refer to your own CA store with the help of an environment variable.