JsonSchemaSubscriber
This form field event subscriber is used to rewrite the JSON Schema $schema keyword property, since the dollar sign is not allowed to be used in form field names.
Basic Usage
By default, the submitted $schema data is rewritten to map to the schema field:
$builder
    ->add('schema', TextType::class)
    ->addEventSubscriber(new JsonSchemaSubscriber());
It is also possible to rewrite $schema to map it to any other field:
$builder
    ->add('jsonSchema', TextType::class)
    ->addEventSubscriber(new JsonSchemaSubscriber('jsonSchema'));