Generate proper documentation/schema for plugin properties using an `anyOf` Schema

[yuri1969]

Describe the issue

Dynamic plugin properties are often additionally typed as String due using Pebble values. This leads to using anyOf in the @Schema definition.

Using an enum as the type doesn't render the plugin property documentation correctly - the Type is duplicated and, more importantly, there are no enum's Possible values listed.

---

A simple demonstration:

test: "{{ input.test }}"

@Schema(
        title = "Dynamic enum property",
        anyOf = {
                String.class,
                TestEnum.class
        }
)
@PluginProperty(
        dynamic = true
)
@Builder.Default
protected Object test = TestEnum.INPUT;

enum TestEnum {
        INPUT,
        OUTPUT
}

Environment

• Kestra Version: 0.16-SNAPSHOT as of Mar 22nd 2024
• Operating System (OS/Docker/Kubernetes):
• Java Version (if you don't run kestra in Docker):