Feature/get graph data from gap

mapping_provider/api/network_graph.py

+from fastapi import APIRouter
+
+from mapping_provider.dependencies import config_dep
+from mapping_provider.services.gap import load_routers, load_trunks
+
+router = APIRouter()
+
+
+@router.get("/network-graph")
+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)}