h52nx: add a warning if the key used for flat-titles is not the expected/recommanded one

nxtomomill/io/config.py

@@ -1111,6 +1111,13 @@ class TomoHDF5Config:
                     flat_titles = convert_str_to_tuple(flat_titles, none_if_empty=True)
                     self.flat_titles = flat_titles
                     flat_title_key_picked = alias
+        if (
+            flat_title_key_picked is not None
+            and flat_title_key_picked != TomoHDF5Config.FLAT_TITLES_DK
+        ):
+            _logger.warning(
+                f"{flat_title_key_picked} will be removed in the future. Please use {TomoHDF5Config.FLAT_TITLES_DK} instead"
+            )
         # handle projection titles. empty string is consider as a valid value
         proj_titles = dict_.get(TomoHDF5Config.PROJ_TITLES_DK, None)
         if proj_titles is not None: