Add a warning about a low image DPI which may cause OCR to fail

src/paperless_tesseract/parsers.py

@@ -244,6 +244,10 @@ class RasterisedDocumentParser(DocumentParser):
                     f"no DPI information is present in this image and "
                     f"OCR_IMAGE_DPI is not set.",
                 )
+            if ocrmypdf_args["image_dpi"] < 70:  # pragma: nocover
+                self.log.warning(
+                    f"Image DPI of {ocrmypdf_args['image_dpi']} is low, OCR may fail",
+                )
 
         if settings.OCR_USER_ARGS and not safe_fallback:
             try: