feat: support cohere rerank

dto/rerank.go

@@ -0,0 +1,19 @@
+package dto
+
+type RerankRequest struct {
+	Documents []any  `json:"documents"`
+	Query     string `json:"query"`
+	Model     string `json:"model"`
+	TopN      int    `json:"top_n"`
+}
+
+type RerankResponseDocument struct {
+	Document       any     `json:"document"`
+	Index          int     `json:"index"`
+	RelevanceScore float64 `json:"relevance_score"`
+}
+
+type RerankResponse struct {
+	Results []RerankResponseDocument `json:"results"`
+	Usage   Usage                    `json:"usage"`
+}