Tutor was making many calls to iter_installed (~100 on my machine with a
dozen installed plugins). Turns out it's useless to cache Plugin and
Renderer instances, as the config keeps changing all the time. Instead,
we cache the list of installed plugins, which does not change in the
course of a single run.
On my machine this speeds up `tutor config save` by 5x, going from 7.5s
to 1.3s.
Clarify a few variable names, make code more modular. Also, the Renderer
class now makes more sense as a singleton. We took the opportunity to
delete quite a lot of code.
This is for supporting json-based plugins. The great thing about this
change is that it allows us to easily print plugin version numbers in
`plugins list`.
This commit introduces many changes:
- a fully functional minio plugin for local installation
- an almost-functional native k8s deployment
- a new way to process configuration, better suited to plugins
There are still many things to do:
- get rid of all the TODOs
- get a fully functional minio plugin for k8s
- add documentation for pluginso
- ...
