[Ftr] Improve integration suite with file downloads

[l3nz]

Is your feature request related to a problem? Please describe.

It is important to have an integration suite that actually exercises important features. At the moment we don't exercise HTTP download for CLJS and no file download/coercion (JSON, YAML, etc) for CLJ.

Describe the solution you'd like

One could download files from GitHub, e.g. from here: https://github.com/l3nz/cli-matic/tree/master/examples-cljs-planck/data

This should work trivially when replicating https://github.com/l3nz/cli-matic/blob/master/examples-cljs-planck/read-file.cljs in the CLJ area.

The problem is that the world is HTTPS now, and Planck crashes on HTTPS. Any chance of downloading from GitHub as HTTP?

Tests are to be added at https://github.com/l3nz/cli-matic/blob/a4ccc97c410e0501c967adbffd2a3fe3da5fde7a/scriptTester.sh#L191

[l3nz]

Maybe this could hlp somehow? https://docs.postman-echo.com/?version=latest