Basic discussions forum framework

Adds the basic structure for the Discussions MFE around which future development
will happen.

src/discussions/posts/data/slices.js

@@ -0,0 +1,55 @@
+/* eslint-disable no-param-reassign,import/prefer-default-export */
+import { createSlice } from '@reduxjs/toolkit';
+import { LoadingStatus } from '../../../data/constants';
+
+function normaliseThreads(rawThreadsData) {
+  const topicThreadMap = {};
+  rawThreadsData.forEach(
+    thread => {
+      if (!topicThreadMap[thread.topic_id]) {
+        topicThreadMap[thread.topic_id] = [];
+      }
+      topicThreadMap[thread.topic_id].push(thread);
+    },
+  );
+  return topicThreadMap;
+}
+
+const courseThreadsSlice = createSlice({
+  name: 'courseThreads',
+  initialState: {
+    status: LoadingStatus.LOADING,
+    page: null,
+    threads: {
+      // Mapping of topic ids to threads in them
+    },
+    totalPages: null,
+    totalThreads: null,
+  },
+  reducers: {
+    fetchCourseThreadsRequest: (state) => {
+      state.status = LoadingStatus.LOADING;
+    },
+    fetchCourseThreadsSuccess: (state, { payload }) => {
+      state.status = LoadingStatus.LOADED;
+      state.threads = normaliseThreads(payload.results);
+      state.page = payload.pagination.page;
+      state.totalPages = payload.pagination.num_pages;
+      state.totalThreads = payload.pagination.count;
+    },
+    fetchCourseThreadsFailed: (state) => {
+      state.status = LoadingStatus.FAILED;
+    },
+    fetchCourseThreadsDenied: (state) => {
+      state.status = LoadingStatus.DENIED;
+    },
+  },
+});
+
+export const {
+  fetchCourseThreadsRequest,
+  fetchCourseThreadsSuccess,
+  fetchCourseThreadsFailed,
+} = courseThreadsSlice.actions;
+
+export const courseThreadsReducer = courseThreadsSlice.reducer;