Add unkown fields as default phrase entry

Signed-off-by: Dominik Voigt <dominik.ingo.voigt@gmail.com>

src/main/java/org/jabref/logic/importer/fetcher/ComplexSearchQuery.java

@@ -42,6 +42,7 @@ public static ComplexSearchQuery fromTerms(Collection<Term> terms) {
                 case "year" -> builder.singleYear(Integer.valueOf(termText));
                 case "year-range" -> builder.parseYearRange(termText);
                 case "default" -> builder.defaultFieldPhrase(termText);
+                default -> builder.defaultFieldPhrase(term.field() + ":" + termText);
             }
         });
         return builder.build();