add merging sentences action

sentence_api/main.py

@@ -565,6 +565,27 @@ def create_app(
             raise HTTPException(status_code=404, detail="Sentence was not found.")
         return result
 
+
+    @application.put(
+        "/api/v1/admin/videos/{video_hash}/sentences/{sentence_index}/merge",
+        response_model=SentenceBoundary,
+        dependencies=[Depends(require_admin)],
+    )
+    def merge_sentence(
+        video_hash: str = SHA256_PATH,
+        sentence_index: int = ApiPath(ge=0),
+    ) -> SentenceBoundary:
+        try:
+            sentence = video_repository.merge_with_next_sentence(
+                video_hash,
+                sentence_index,
+            )
+        except ValueError as exc:
+            raise HTTPException(status_code=400, detail=str(exc)) from exc
+        if sentence is None:
+            raise HTTPException(status_code=404, detail="Sentence was not found.")
+        return sentence
+
     @application.put(
         "/api/v1/admin/videos/{video_hash}/sentences/{sentence_index}/boundary",
         response_model=List[SentenceBoundary],