feat: add experimental_personalization_api_key feature to RoFeatures

- Add MEILI_EXPERIMENTAL_PERSONALIZATION_API_KEY environment variable
- Add experimental_personalization_api_key field to Opt struct with CLI and env support
- Add experimental_personalization_api_key field to InstanceTogglableFeatures
- Store personalization API key in FeatureData for access through IndexScheduler
- Add experimental_personalization_api_key() method to IndexScheduler
- Update analytics destructuring to include new field
- Maintain RoFeatures Copy trait while properly handling Option<String>

crates/meilisearch-types/src/features.rs

@@ -25,11 +25,12 @@ pub struct RuntimeTogglableFeatures {
     pub multimodal: bool,
 }
 
-#[derive(Default, Debug, Clone, Copy)]
+#[derive(Default, Debug, Clone)]
 pub struct InstanceTogglableFeatures {
     pub metrics: bool,
     pub logs_route: bool,
     pub contains_filter: bool,
+    pub experimental_personalization_api_key: Option<String>,
 }
 
 #[derive(Serialize, Deserialize, Debug, Clone, PartialEq, Eq)]