This filter folds Scandinavian characters åÅäæÄÆ->a and öÖøØ->o.
It also discriminate against use of double vowels aa, ae, ao, oe and oo, leaving just the first one.
It's is a semantically more destructive solution than
ScandinavianNormalizationFilter but
can in addition help with matching raksmorgas as räksmörgås.
blåbærsyltetøj == blåbärsyltetöj == blaabaarsyltetoej == blabarsyltetoj
räksmörgås == ræksmørgås == ræksmörgaos == raeksmoergaas == raksmorgas
Background:
Swedish åäö are in fact the same letters as Norwegian and Danish åæø and thus interchangeable
when used between these languages. They are however folded differently when people type
them on a keyboard lacking these characters.
In that situation almost all Swedish people use a, a, o instead of å, ä, ö.
Norwegians and Danes on the other hand usually type aa, ae and oe instead of å, æ and ø.
Some do however use a, a, o, oo, ao and sometimes permutations of everything above.
This filter solves that mismatch problem, but might also cause new.