refactor thumbnails

Signed-off-by: Christian Richter <crichter@owncloud.com>

extensions/thumbnails/pkg/thumbnail/imgsource/imgsource.go

@@ -0,0 +1,31 @@
+package imgsource
+
+import (
+	"context"
+	"io"
+)
+
+type key int
+
+const (
+	auth key = iota
+)
+
+// Source defines the interface for image sources
+type Source interface {
+	Get(ctx context.Context, path string) (io.ReadCloser, error)
+}
+
+// ContextSetAuthorization puts the authorization in the context.
+func ContextSetAuthorization(parent context.Context, authorization string) context.Context {
+	return context.WithValue(parent, auth, authorization)
+}
+
+// ContextGetAuthorization gets the authorization from the context.
+func ContextGetAuthorization(ctx context.Context) (string, bool) {
+	val := ctx.Value(auth)
+	if val == nil {
+		return "", false
+	}
+	return val.(string), true
+}