cubicweb #2514939 unique together constraint may silently truncate index names [validation pending]

over 60 char the index name is truncated leading dropping the _idx suffix.

The code that promotes integrity error to unique together constraint then fails to recognize them.

priorityimportant
typebug
done in3.18.0
load2.000
load left0.000
closed by#8e88576787c3 [schema] fix unique together index handling
patch[schema] fix unique together index handling [applied]