restructure model_metrics_sources to use type + provider pattern

crates/common/src/configuration.rs

@@ -127,32 +127,39 @@ pub struct TopLevelRoutingPreference {
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
-pub struct MetricsAuth {
-    #[serde(rename = "type")]
-    pub auth_type: String, // only "bearer" supported
-    pub token: String,
+#[serde(tag = "type", rename_all = "snake_case")]
+pub enum MetricsSource {
+    Cost(CostMetricsConfig),
+    Latency(LatencyMetricsConfig),
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
-#[serde(tag = "type", rename_all = "snake_case")]
-pub enum MetricsSource {
-    CostMetrics {
-        url: String,
-        refresh_interval: Option<u64>,
-        auth: Option<MetricsAuth>,
-    },
-    PrometheusMetrics {
-        url: String,
-        query: String,
-        refresh_interval: Option<u64>,
-    },
-    #[serde(rename = "digitalocean_pricing")]
-    DigitalOceanPricing {
-        refresh_interval: Option<u64>,
-        /// Map DO catalog keys (`lowercase(creator)/model_id`) to Plano model names.
-        /// Example: `openai/openai-gpt-oss-120b: openai/gpt-4o`
-        model_aliases: Option<HashMap<String, String>>,
-    },
+pub struct CostMetricsConfig {
+    pub provider: CostProvider,
+    pub refresh_interval: Option<u64>,
+    /// Map DO catalog keys (`lowercase(creator)/model_id`) to Plano model names.
+    /// Example: `openai/openai-gpt-oss-120b: openai/gpt-4o`
+    pub model_aliases: Option<HashMap<String, String>>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum CostProvider {
+    Digitalocean,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LatencyMetricsConfig {
+    pub provider: LatencyProvider,
+    pub url: String,
+    pub query: String,
+    pub refresh_interval: Option<u64>,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum LatencyProvider {
+    Prometheus,
 }
 
 #[derive(Debug, Clone, Serialize, Deserialize)]