feat(thumbnails): optional libvips based thumbnail generation

Can be enabled by setting the 'enable_vips' tag on 'go build'

services/thumbnails/pkg/preprocessor/preprocessor_imaging.go

@@ -1,3 +1,5 @@
+//go:build !enable_vips
+
 package preprocessor
 
 import (

services/thumbnails/pkg/preprocessor/preprocessor_vips.go

@@ -0,0 +1,20 @@
+//go:build enable_vips
+
+package preprocessor
+
+import (
+	"io"
+
+	"github.com/davidbyttow/govips/v2/vips"
+)
+
+func init() {
+	vips.LoggingSettings(nil, vips.LogLevelError)
+}
+
+type ImageDecoder struct{}
+
+func (v ImageDecoder) Convert(r io.Reader) (interface{}, error) {
+	img, err := vips.NewImageFromReader(r)
+	return img, err
+}