TextAnalyzerConfiguration class Null safety

An interface exposing language properties used in text analysis:

• characterFilter is a function that manipulates text prior to stemming and tokenization;
• termFilter is a filter function that returns a collection of terms from a term. It returns an empty collection if the term is to be excluded from analysis or, returns multiple terms if the term is split (e.g. at hyphens) and / or, returns modified term(s), such as applying a stemmer algorithm; and
• termSplitter returns a list of terms from text.