public DockerFileBuilder assemblyUser(String assemblyUser) {
        this.assemblyUser = assemblyUser;
        return this;
    }
Escape any slashes, quotes, and newlines int the value.  If any escaping occurred, quote the value.
@param key The key
@param value The value
@return Escaped and quoted key="value"
src/main/java/io/fabric8/maven/docker/assembly/DockerFileBuilder.java