Add GraphTopology trait and use it to interface graph model with algorithm

tests/dijkstra.rs

@@ -1,6 +1,6 @@
 use grapherity::algorithms;
 use grapherity::models::Graph;
-use grapherity::models::Vertex;
+use grapherity::traits::GraphTopology;
 
 #[test]
 fn dijkstra_single_vertex() {
@@ -107,9 +107,9 @@ fn dijkstra() {
     }
 }
 
-fn make_test_graph() -> (Graph, [Vertex; 10]) {
+fn make_test_graph() -> (Graph, [<Graph as GraphTopology>::Vertex; 10]) {
     let mut graph = Graph::new();
-    let vertices: [Vertex; 10] = core::array::from_fn(|_| graph.add_vertex());
+    let vertices = core::array::from_fn::<_, 10, _>(|_| graph.add_vertex());
     graph.add_edge(vertices[0], vertices[1]);
     graph.add_edge(vertices[1], vertices[2]);
     graph.add_edge(vertices[1], vertices[3]);