Feat: support cross-lang search. (#7557)

### What problem does this PR solve?

#7376
#4503
#5710 
#7470

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

api/apps/chunk_app.py

@@ -22,7 +22,7 @@ from flask_login import login_required, current_user
 from rag.app.qa import rmPrefix, beAdoc
 from rag.app.tag import label_question
 from rag.nlp import search, rag_tokenizer
-from rag.prompts import keyword_extraction
+from rag.prompts import keyword_extraction, cross_languages
 from rag.settings import PAGERANK_FLD
 from rag.utils import rmSpace
 from api.db import LLMType, ParserType
@@ -275,6 +275,7 @@ def retrieval_test():
     vector_similarity_weight = float(req.get("vector_similarity_weight", 0.3))
     use_kg = req.get("use_kg", False)
     top = int(req.get("top_k", 1024))
+    langs = req.get("cross_languages", [])
     tenant_ids = []
 
     try:
@@ -294,6 +295,9 @@ def retrieval_test():
         if not e:
             return get_data_error_result(message="Knowledgebase not found!")
 
+        if langs:
+            question = cross_languages(kb.tenant_id, None, question, langs)
+
         embd_mdl = LLMBundle(kb.tenant_id, LLMType.EMBEDDING.value, llm_name=kb.embd_id)
 
         rerank_mdl = None