[Router] Refactor protocol definitions: split spec.rs into modular files (#11677)

Co-authored-by: Chang Su <chang.s.su@oracle.com>

sgl-router/src/protocols/embedding.rs

@@ -0,0 +1,57 @@
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+
+use super::common::GenerationRequest;
+
+// ============================================================================
+// Embedding API
+// ============================================================================
+
+#[derive(Debug, Clone, Deserialize, Serialize)]
+pub struct EmbeddingRequest {
+    /// ID of the model to use
+    pub model: String,
+
+    /// Input can be a string, array of strings, tokens, or batch inputs
+    pub input: Value,
+
+    /// Optional encoding format (e.g., "float", "base64")
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub encoding_format: Option<String>,
+
+    /// Optional user identifier
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub user: Option<String>,
+
+    /// Optional number of dimensions for the embedding
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub dimensions: Option<u32>,
+
+    /// SGLang extension: request id for tracking
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub rid: Option<String>,
+}
+
+impl GenerationRequest for EmbeddingRequest {
+    fn is_stream(&self) -> bool {
+        // Embeddings are non-streaming
+        false
+    }
+
+    fn get_model(&self) -> Option<&str> {
+        Some(&self.model)
+    }
+
+    fn extract_text_for_routing(&self) -> String {
+        // Best effort: extract text content for routing decisions
+        match &self.input {
+            Value::String(s) => s.clone(),
+            Value::Array(arr) => arr
+                .iter()
+                .filter_map(|v| v.as_str())
+                .collect::<Vec<_>>()
+                .join(" "),
+            _ => String::new(),
+        }
+    }
+}