Feature: View a contact's previous conversation (#422)

* Add API to fetch conversations of a contact

* Add conversation list in sidebar

app/javascript/dashboard/store/modules/contactConversations.js

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+import Vue from 'vue';
+import * as types from '../mutation-types';
+import ContactAPI from '../../api/contacts';
+
+const state = {
+  records: {},
+  uiFlags: {
+    isFetching: false,
+  },
+};
+
+export const getters = {
+  getUIFlags($state) {
+    return $state.uiFlags;
+  },
+  getContactConversation: $state => id => {
+    return $state.records[Number(id)] || [];
+  },
+};
+
+export const actions = {
+  get: async ({ commit }, contactId) => {
+    commit(types.default.SET_CONTACT_CONVERSATIONS_UI_FLAG, {
+      isFetching: true,
+    });
+    try {
+      const response = await ContactAPI.getConversations(contactId);
+      commit(types.default.SET_CONTACT_CONVERSATIONS, {
+        id: contactId,
+        data: response.data.payload,
+      });
+      commit(types.default.SET_ALL_CONVERSATION, response.data.payload, {
+        root: true,
+      });
+      commit(types.default.SET_CONTACT_CONVERSATIONS_UI_FLAG, {
+        isFetching: false,
+      });
+    } catch (error) {
+      commit(types.default.SET_CONTACT_CONVERSATIONS_UI_FLAG, {
+        isFetching: false,
+      });
+    }
+  },
+};
+
+export const mutations = {
+  [types.default.SET_CONTACT_CONVERSATIONS_UI_FLAG]($state, data) {
+    $state.uiFlags = {
+      ...$state.uiFlags,
+      ...data,
+    };
+  },
+  [types.default.SET_CONTACT_CONVERSATIONS]: ($state, { id, data }) => {
+    Vue.set($state.records, id, data);
+  },
+};
+
+export default {
+  namespaced: true,
+  state,
+  getters,
+  actions,
+  mutations,
+};