FormRules class

A small fluent helper to build validation rules for controls inside a FormGroup, with support for cross-field dependencies.

Why this exists:

• dart_ng_forms allows attaching a single validator to a control.
• In real forms, you often need to compose multiple validators and also re-validate a field when other fields change (cross-field rules).

Example:

final rules = FormRules(form);

rules.ruleFor<String>('password')
  .compose(notEmpty)
  .compose(minLength8)
  .dependsOn('username'); // re-validates password when username changes

// later...
rules.dispose();