feat: support /v1/rerank router

relay/model/rerank.go

@@ -0,0 +1,10 @@
+package model
+
+type RerankRequest struct {
+	Model           string   `json:"model"`
+	Documents       []string `json:"documents"`
+	Query           string   `json:"query"`
+	TopN            *int     `json:"top_n,omitempty"`
+	MaxChunksPerDoc *int     `json:"max_chunks_per_doc,omitempty"`
+	ReturnDocuments *bool    `json:"return_documents,omitempty"`
+}