Use PlanType enum when formatting usage-limit CTA (#3495)

- Started using Play type struct
- Added CTA for team/business 
- Refactored a bit to unify the logic

codex-rs/core/src/token_data.rs

@@ -47,15 +47,6 @@ pub(crate) enum PlanType {
     Unknown(String),
 }
 
-impl PlanType {
-    pub fn as_string(&self) -> String {
-        match self {
-            Self::Known(known) => format!("{known:?}").to_lowercase(),
-            Self::Unknown(s) => s.clone(),
-        }
-    }
-}
-
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
 #[serde(rename_all = "lowercase")]
 pub(crate) enum KnownPlan {