Support for sub-commands related to modules

[janmedrek]

Description

Every Kyma module will require some configuration and setup, we want the users to have a single tool that they will be able to use during their development. Since configuration/setup flows and parameters will differ from module to module, there is no single way of handling those. We would need more of a modular approach when it comes to interacting with modules.

One of the solutions would be to introduce a sub-command framework that the module developers would be able to leverage in order to provide their own sub-commands for the CLI. Just like Busola's widgets, we could then present those as a single tool containing multiple packages related to specific modules (and have a semi-modular CLI as a side effect).

Acceptance Criteria

• [ ] CLI supports "pluggable" sub-commands related to modules
• [ ] Module developers are able to create their own sets of sub-commands per module they are delivering
• [ ] Technical guide for creating sub-commands is available

Reasons

We want the users to be able to configure specific modules via a single tool (the CLI).