Well, turns out radian Emacs config provides an advice for such things:
(dolist (func '(define-minor-mode))
(advice-add func :around #'radian--advice-silence-messages))
which you can add to your init.local.el.
Here is its definition:
(defun radian--advice-silence-messages (func &rest args)
"Invoke FUNC with ARGS, silencing all messages. This is ...
You're using Emacs 26, and the cl-lib version you're referring to is for Emacs 24. Use the built-in package manager: M-x list-packages.
Emacs 26 will probably have cl-lib 1.0 already installed.
The soap-client you're referring to in github is old (ie. not v3.2.0).
If you have older versions installed, un-install them.
Something that is deprecated is not unsupported. So it's not true that you cannot use it.
A warning is not, at least in Emacs, an error. It's just a message to let you know something you might not otherwise be aware of. And many, many Emacs warnings are benign in actual use, for various reasons. You need to understand a warning, and do so in the context ...