Draw front lines on the react map.

https://github.com/dcs-liberation/dcs_liberation/issues/2039

client/src/api/frontLinesSlice.ts

@@ -0,0 +1,28 @@
+import { PayloadAction, createSlice } from "@reduxjs/toolkit";
+
+import FrontLine from "./frontline";
+import { RootState } from "../app/store";
+
+interface FrontLinesState {
+  fronts: FrontLine[];
+}
+
+const initialState: FrontLinesState = {
+  fronts: [],
+};
+
+export const frontLinesSlice = createSlice({
+  name: "frontLines",
+  initialState,
+  reducers: {
+    setFrontLines: (state, action: PayloadAction<FrontLine[]>) => {
+      state.fronts = action.payload;
+    },
+  },
+});
+
+export const { setFrontLines } = frontLinesSlice.actions;
+
+export const selectFrontLines = (state: RootState) => state.frontLines;
+
+export default frontLinesSlice.reducer;

client/src/api/frontline.ts

@@ -0,0 +1,7 @@
+import { LatLng } from "leaflet";
+
+export interface FrontLine {
+  extents: LatLng[];
+}
+
+export default FrontLine;