Implement validation feedback

[achobanov]

Overview

The domain validation is based on exceptions. In Setup domain this is handled in our Form framework using the Mud input validation mechanism. However we don't have any handling for property-agnostic validations and NO validation handling in Dashboard whatsoever. This will be a nightmare to work with during Asenovgrad.

Solution

Notifier

Implement some kind of toast notifier - Mud offers a Popover component to display the messages. We need:

1. Error message
2. Validation message
3. Successful message

Handle DomainException

Use try-catch to swallow any propagation of DomainException and render the message using the Notifier. This has to be done at the level of Behinds.

[achobanov]

While not ideal this can be a robust solution if implemented uniformly. Investigation into a more centralized error handling using Blazor's ErrorBoundary components: #286