Thesaurus values can have duplicates with different lower and upper case combinations

[RafaPolit]

Describe the bug
As of today, we accept duplicated values for thesaurus as long as they have a different upper and lower case configuration. So, for us, these thesaurus values are ALL different to one another, and actually create different translations keys matching the upper and lower case values:

• Yes
• yes
• YES
• no
• No
• NO

A thesaurus with these values, will actually have 6 different values and 6 different translation keys. This somehow feels like the wrong approach.

[aphilop]

First do a quick analysis of who has same name siblings at the same level.