Add support for Dockerfile templates
This merge request makes it possible to fetch a Git repository of a runtime from GitLab / GitHub.
Files in from this repository are going to be loaded into memory, what makes it possible to access them quickly and eventually use this to parse a
Dockerfile template and start a build process.
In this merge request we are going to add support for using
text/template templating system inside a Dockerfile to generate its content depending on build context (like serverless function name, all the variables and inputs we have available at the build time).