* Bootstrap OpenAPI Funnel schemas

* Implement Plugins API Funnel view

* Allow casting funnel step directly from `%Goal{}`

* Check feature availability on funnel creation

just like it's done when inserting goals

* Implement Plugins API context module for Funnels

* Implement GET/PUT funnels via Plugins API

* Fix typo

* A rare event in which dialyzer found an actual bug, wow!

* Format

* Wrap creation request with a root `funnel` key

* Format

* Extract common funnel get query

* Remove redundant tag

* Refactor queries a bit