Task: Unify request interfaces

Currently, visitor requests and entry/exit requests are separate entities (due to specific customer business requirements and separate allowed/disallowed permissions). Historically, different pages and forms were used to work with these different request types. We certainly won't change the business logic and architecture, but we can and should unify the interfaces. We will make the creation form universal by simply adding a switch for "Material" or "Visitor only" (just to correctly check if the form is filled out, so that a user doesn't create a visitor-only request while forgetting to specify what they want to bring in or take out, without the form highlighting it). For the output, we can use a single interface utilizing union objects in GraphQL.