Feature/get graph data from gap

mapping_provider/api/network_graph.py

@@ -7,5 +7,6 @@ router = APIRouter()
 
 
 @router.get("/network-graph")
-def get_network_graph(config: config_dep):
+def get_network_graph(config: config_dep) -> dict[str, list[str] | list[list[str]]]:
+    """Network graph endpoint."""
     return {"routers": load_routers(config), "trunks": load_trunks(config)}