How to make fields required based on a boolean value in a Slack thread.

defineField({
      title: "Enable cookie banner",
      name: "cookie_banner_enabled",
      type: "boolean",
      group: "cookies"
    }),
    defineField({
      title: "Cookie banner title",
      description: "The title of the cookie banner",
      name: "cookie_banner_title",
      type: "string",
      group: "cookies",
      hidden: ({ document }) => !document?.cookie_banner_enabled
    }),
    defineField({
      title: "Cookie banner button text",
      description: "The text of the cookie banner button if empty defaults to 'Accepteren'",
      name: "cookie_banner_button_text",
      type: "string",
      group: "cookies",
      hidden: ({ document }) => !document?.cookie_banner_enabled
    }),
    defineField({
      title: "Privacy Policy link text",
      description: "The privacy policy link text if empty defaults to 'Privacy Policy'",
      name: "privacy_link_text",
      type: "string",
      group: "cookies",
      hidden: ({ document }) => !document?.cookie_banner_enabled
    }),
    defineField({
      title: "Privacy Policy URL",
      description: "The URL to your privacy policy page.",
      name: "privacy_url",
      type: "reference",
      group: "cookies",
      to: [{ type: "page" }],
      hidden: ({ document }) => !document?.cookie_banner_enabled
    }),

            validation: (Rule) => Rule.custom((value, context) => {
                if (context.parent.externalLink) {
                    return true
                }

                if (!value) return "This field is required"

                return true
            }),

defineField({
      title: "Cookie banner title",
      description: "The title of the cookie banner",
      name: "cookie_banner_title",
      type: "string",
      group: "cookies",
      hidden: ({ document }) => !document?.cookie_banner_enabled,
      validation: (Rule) =>
        Rule.custom((value, context) => {
          if (value && context?.document?.cookie_banner_enabled) {
            return true
          }

          if (!value) return "This field is required"

          return true
        })
    }),

defineField({
      title: "Cookie banner title",
      description: "The title of the cookie banner",
      name: "cookie_banner_title",
      type: "string",
      group: "cookies",
      hidden: ({ document }) => !document?.cookie_banner_enabled,
      validation: (Rule) =>
        Rule.custom((value, context) => {
          if (context?.document?.cookie_banner_enabled && !value) {
            return "Cookie banner title is required"
          }

          return true
        })
    }),