feat(rerankers): Add new backend, support jina rerankers API (#2121)

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/schema/jina.go

@@ -0,0 +1,34 @@
+package schema
+
+// RerankRequest defines the structure of the request payload
+type JINARerankRequest struct {
+	Model     string   `json:"model"`
+	Query     string   `json:"query"`
+	Documents []string `json:"documents"`
+	TopN      int      `json:"top_n"`
+}
+
+// DocumentResult represents a single document result
+type JINADocumentResult struct {
+	Index          int      `json:"index"`
+	Document       JINAText `json:"document"`
+	RelevanceScore float64  `json:"relevance_score"`
+}
+
+// Text holds the text of the document
+type JINAText struct {
+	Text string `json:"text"`
+}
+
+// RerankResponse defines the structure of the response payload
+type JINARerankResponse struct {
+	Model   string               `json:"model"`
+	Usage   JINAUsageInfo        `json:"usage"`
+	Results []JINADocumentResult `json:"results"`
+}
+
+// UsageInfo holds information about usage of tokens
+type JINAUsageInfo struct {
+	TotalTokens  int `json:"total_tokens"`
+	PromptTokens int `json:"prompt_tokens"`
+}