Split action

<details>
  <summary>A draft invoice's actions</summary>
  <Kit.Phoenix.Roles.ActionGroup.action_group>
    <:lead
      action="primary-action"
      id="role-split-action-send"
      label="More ways to send"
      variants={[
        Kit.Phoenix.Menu.group([
          Kit.Phoenix.Menu.item("Send and mark as paid"),
          Kit.Phoenix.Menu.item("Schedule sending…")
        ])
      ]}
    >Send invoice</:lead>
    <:secondary
      action="secondary-action"
      id="role-split-action-save"
      label="More ways to save"
      variants={[
        Kit.Phoenix.Menu.group([
          Kit.Phoenix.Menu.item("Save as a template"),
          Kit.Phoenix.Menu.item("Save a copy as a new draft")
        ])
      ]}
    >Save as draft</:secondary>
  </Kit.Phoenix.Roles.ActionGroup.action_group>
</details>

<details>
  <summary>An invoice being sent</summary>
  <Kit.Phoenix.Roles.ActionGroup.action_group>
    <:lead
      action="primary-action"
      id="role-split-action-sending"
      label="More ways to send"
      variants={[
        Kit.Phoenix.Menu.group([
          Kit.Phoenix.Menu.item("Send and mark as paid"),
          Kit.Phoenix.Menu.item("Schedule sending…")
        ])
      ]}
      action_state={Kit.Phoenix.ActionState.submitting()}
    >Send invoice</:lead>
  </Kit.Phoenix.Roles.ActionGroup.action_group>
</details>