feat: implemented link previews (server files) (#3073)

* feat: implmented link previews (server files)

* chore: updated variable name

* chore: renamed service file from `metadata_service.go` to `link_service.go`

* fix: passing errors

* fix: fixed linter warnong about `ctx`

server/route/api/v2/link_service.go

@@ -0,0 +1,25 @@
+package v2
+
+import (
+	"context"
+
+	getter "github.com/usememos/memos/plugin/http-getter"
+	apiv2pb "github.com/usememos/memos/proto/gen/api/v2"
+)
+
+func (*APIV2Service) GetMetadata(_ context.Context, request *apiv2pb.GetLinkMetadataRequest) (*apiv2pb.GetLinkMetadataResponse, error) {
+	urlStr := request.Url
+
+	htmlMeta, err := getter.GetHTMLMeta(urlStr)
+	if err != nil {
+		return nil, err
+	}
+
+	return &apiv2pb.GetLinkMetadataResponse{
+		Metadata: &apiv2pb.Metadata{
+			Title:       htmlMeta.Title,
+			Description: htmlMeta.Description,
+			Image:       htmlMeta.Image,
+		},
+	}, nil
+}