Improve support of German compound words in ingredients processing (e.g. Himbeerstücke, Schokoladenstücke)

[stephanegigandet]

For ingredients processing, we currently remove words like "stücke" (from the ingredients_processing.txt taxonomy), and try to match them to ingredients. It does not work very well as some final letters might be added or removed when creating compound words.

e.g. Schokolade -> Schokoladenstücke, Himbeere -> Himbeerstücke

See https://de.openfoodfacts.org/ingredients?filter=st%C3%BCcke for some real world examples.

We can solve this in different ways.

One easy way would be to add the words with added/removed letter as synonyms in the ingredients.txt taxonomy:

de:Himbeere, himbeer
de:Schokolade, Schokoladen

Another way could be to try to add or remove letters when we remove part of words like stücke, to see if we find a matching ingredient. This may or may not be error prone (yielding false positives where we change the ingredient to a different ingredient).

Part of

• 🌍 Make Open Food Facts work well in all countries in the world #5690
• Make Open Food Facts work well in German language countries #9949

[stephanegigandet]

Some examples are listed in https://aclanthology.org/W17-1722.pdf