Environment mode

[quentinovega]

Daikoku can be setup as "environment usage" configuring the tenant.
All Usage plan are now an environment. Environment are a plan but had his own swagger, documentation & testing conf.
It could be nice to report easily conf from an environment to another.
Add a way to display only one env. by selecting one in front page and api pages.

• add env mode in tenant
• list all possible env in tenant (with a default flag for one)
  • if delete => delete all implemented env (with a warning message)
  • if new => api have possibility to implement it
• add optionnal props on UsagePlans
  • swagger
  • docs
  • testing
• display new plans props on frontend
• the properties of the api are those of the default env (if not implemented by api, nothing)
• api have now a selector to implement existing env
• add the ability to import from another env
• add the ability to "upgrade" env (ex: preprod to prod => migrate all docs from preprod to prod)