feat: support cohere rerank

relay/channel/cohere/dto.go

@@ -1,5 +1,7 @@
 package cohere
 
+import "one-api/dto"
+
 type CohereRequest struct {
 	Model       string        `json:"model"`
 	ChatHistory []ChatHistory `json:"chat_history"`
@@ -28,6 +30,19 @@ type CohereResponseResult struct {
 	Meta         CohereMeta `json:"meta"`
 }
 
+type CohereRerankRequest struct {
+	Documents       []any  `json:"documents"`
+	Query           string `json:"query"`
+	Model           string `json:"model"`
+	TopN            int    `json:"top_n"`
+	ReturnDocuments bool   `json:"return_documents"`
+}
+
+type CohereRerankResponseResult struct {
+	Results []dto.RerankResponseDocument `json:"results"`
+	Meta    CohereMeta                   `json:"meta"`
+}
+
 type CohereMeta struct {
 	//Tokens CohereTokens `json:"tokens"`
 	BilledUnits CohereBilledUnits `json:"billed_units"`