@Override
        public boolean equals(Object o) {
            if (o == this) return true;
            if ( ! (o instanceof AnalyzerKey other)) return false;
            return other.language == this.language && other.stemMode == this.stemMode;
        }
Combines the languageCode and the stemMode.
It allows to specify up to 6 (5 StemModes and only language code) analyzers per language.
The `/` is used so that it doesn't conflict with ComponentRegistry keys.
lucene-linguistics/src/main/java/com/yahoo/language/lucene/AnalyzerFactory.java