Knot.x Forms use cases scenarios

**Is your feature request related to a problem? Please describe.**
Knot.x Forms should provide details what problems it solves:
- simple forms with error handling + csrf protection
- multi-step forms that can store state in shared storages like Redis
- complex multi-step forms that behave in different manner based on user input
- mixed front-end forms integration by proxy API (CSRF protection) defined in Open API specification

Guides for front-end and back-end integrations.

Topics to describe:
- forms graph transitions and redirects

**Describe the solution you'd like**
Case by case scenarios that can be reflected in Knot.x Example Project.

Start by reviewing the Knot.x Forms project and the Knot.x Example Project to identify existing guides and examples. Document scenarios for simple, multi-step, conditional, and proxy API forms, including transitions, redirects, storage, CSRF protection, and front-end/back-end integration; done means the requested use cases are covered case by case.

Written by the indexing model from the issue text.