Do not use undocumented Clojure features in template project

[PetrGlad]

Generated project.clj uses undocumented #= reader macro. I would suggest to use enclosing let instead, use hard-code some value or, better yet, make it a template's parameter (since current code makes too many assumptions about environment).

let version would look like

(let [docker-image-name (some-> (str (System/getenv "DEFAULT_DOCKER_REGISTRY") "/")
                                                     "example_team/maratus"))]
  (defproject ...
    ))

BTW, why (str "/") is needed in generated project.clj file?

[lasomethingsomething]

Hey @dryewo, do you agree? If so, maybe @PetrGlad can work on this, or we can add a Help Wanted label?