[Refactor]: Core/API Split (#1506)

Refactors api folder to core, creates firm split between backend code and api frontend.

core/backend/transcription.go

@@ -0,0 +1,52 @@
+package backend
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/go-skynet/LocalAI/core/services"
+	"github.com/go-skynet/LocalAI/pkg/grpc/proto"
+	"github.com/go-skynet/LocalAI/pkg/model"
+	"github.com/go-skynet/LocalAI/pkg/schema"
+)
+
+func ModelTranscription(audio, language string, loader *model.ModelLoader, c schema.Config, o *schema.StartupOptions) (*schema.WhisperResult, error) {
+
+	opts := modelOpts(c, o, []model.Option{
+		model.WithBackendString(model.WhisperBackend),
+		model.WithModel(c.Model),
+		model.WithContext(o.Context),
+		model.WithThreads(uint32(c.Threads)),
+		model.WithAssetDir(o.AssetsDestination),
+		model.WithExternalBackends(o.ExternalGRPCBackends, false),
+	})
+
+	whisperModel, err := loader.BackendLoader(opts...)
+	if err != nil {
+		return nil, err
+	}
+
+	if whisperModel == nil {
+		return nil, fmt.Errorf("could not load whisper model")
+	}
+
+	return whisperModel.AudioTranscription(context.Background(), &proto.TranscriptRequest{
+		Dst:      audio,
+		Language: language,
+		Threads:  uint32(c.Threads),
+	})
+}
+
+func TranscriptionOpenAIRequest(modelName string, input *schema.OpenAIRequest, audioFilePath string, cl *services.ConfigLoader, ml *model.ModelLoader, startupOptions *schema.StartupOptions) (*schema.WhisperResult, error) {
+	config, input, err := ReadConfigFromFileAndCombineWithOpenAIRequest(modelName, input, cl, startupOptions)
+	if err != nil {
+		return nil, fmt.Errorf("failed reading parameters from request:%w", err)
+	}
+
+	tr, err := ModelTranscription(audioFilePath, input.Language, ml, *config, startupOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	return tr, nil
+}