Added Swashbuckle.AspNetCore.Annotations.SwaggerIgnoreAttribute

[jcracknell]

Application of the SwaggerIgnoreAttribute suppresses the annotated property during schema generation, without altering the serialization behavior as with JsonIgnoreAttribute.

This is useful in a scenario where you want to capture and reject unhandled properties, without advertising that you accept additionalProperties (which is the opposite of what is intended):

public abstract class RequestBase : IValidatableObject {
    [SwaggerIgnore]
    [JsonExtensionData]
    public IDictionary<string, JsonElement>? UnsupportedProperties { get; set; }

    public virtual IEnumerable<ValidationResult> Validate(ValidationContext validationContext) {
        if(UnsupportedProperties is { Count: not 0 })
            foreach(var entry in UnsupportedProperties)
                yield return new ValidationResult($"Unsupported property: {entry.Key}.", new[] { entry.Key });
    }
}

I added the annotation to the Swashbuckle.AspNetCore.SwaggerGen project as it is much easier to filter the properties in the JsonSerializerDataContractResolver than after the fact in a filter, as you would need to regenerate the data contract for the type and then remove all of the annotated properties and derived side effects.