Add support for ytt for templating

[cppforlife]

ytt (https://get-ytt.io; https://github.com/k14s/ytt) is a yaml templating tool that works directly with yaml structures unlike other common templating tools that work with text. by working with structures, ytt avoids problems with yaml escaping, indentation, etc.

it would be nice to allow kapitan to use ytt for templating configuration.

[uberspot]

Just to verify, when you say allow kapitan to use ytt for templating configuration do you mean be able to write the inventory in 'ytt' syntax? Or do you mean to be able to process templates written in ytt as a new kapitan input type (like jsonnet, jinja2, kadet, helm etc).

The first option would require writing something that would translate ytt templates in the inventory to re-class compatible yaml. The second would need a new input type defined.

Any other ideas are welcome.

[ademariag]

From earlier conversation (I proposed/suggested the integration) I think what we want is to evaluate "to be able to process templates written in ytt as a new kapitan input type (like jsonnet, jinja2, kadet, helm etc).|

[logdnalf]

I am also interested in this feature. Jsonnet has a steep learning curve and not everyone is familiar with it. Similar with Python. Having a YAML-based templating (not Jinja2) would make adoption of Kapitan easier.