Add gRPC authentication

[sr-gi]

Currently, the gRPC API is non-authenticated, meaning that anyone could manage the tower if the API was offered outside localhost. This is obviously not safe, so gRPC TLS Auth needs to be added.

In the meantime, the RPC interface MUST NOT be advertised outside localhost.

[sr-gi]

@orbitalturtle started working on this in the old python codebase. If you, eager new contributor, are considering tackling this it may be a good idea to take a look at her approach: talaia-labs/python-teos#262

[orbitalturtle]

Giving this a go :)

[sr-gi]

Yaaay! Happy to have you around 😁