feat: add inpaint mask generation functionality

uses rembg, see https://github.com/danielgatis/rembg

extras/inpaint_mask.py

@@ -0,0 +1,15 @@
+from rembg import remove, new_session
+
+
+def generate_mask_from_image(image, mask_model):
+    if image is None:
+        return
+
+    if 'image' in image:
+        image = image['image']
+
+    return remove(
+        image,
+        session=new_session(mask_model),
+        only_mask=True
+    )