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

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

core/backend/rerank.go

@@ -0,0 +1,39 @@
+package backend
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/go-skynet/LocalAI/core/config"
+	"github.com/go-skynet/LocalAI/pkg/grpc/proto"
+	model "github.com/go-skynet/LocalAI/pkg/model"
+)
+
+func Rerank(backend, modelFile string, request *proto.RerankRequest, loader *model.ModelLoader, appConfig *config.ApplicationConfig, backendConfig config.BackendConfig) (*proto.RerankResult, error) {
+	bb := backend
+	if bb == "" {
+		return nil, fmt.Errorf("backend is required")
+	}
+
+	grpcOpts := gRPCModelOpts(backendConfig)
+
+	opts := modelOpts(config.BackendConfig{}, appConfig, []model.Option{
+		model.WithBackendString(bb),
+		model.WithModel(modelFile),
+		model.WithContext(appConfig.Context),
+		model.WithAssetDir(appConfig.AssetsDestination),
+		model.WithLoadGRPCLoadModelOpts(grpcOpts),
+	})
+	rerankModel, err := loader.BackendLoader(opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	if rerankModel == nil {
+		return nil, fmt.Errorf("could not load rerank model")
+	}
+
+	res, err := rerankModel.Rerank(context.Background(), request)
+
+	return res, err
+}