feat: Add language selector

Closes #212

client/src/sagas/core/services/core.js

@@ -4,7 +4,6 @@ import { fetchCoreRequest } from '../requests';
 import { initializeCore } from '../../../actions';
 import i18n from '../../../i18n';
 
-// eslint-disable-next-line import/prefer-default-export
 export function* initializeCoreService() {
   const {
     user,
@@ -25,6 +24,7 @@ export function* initializeCoreService() {
     notifications,
   } = yield call(fetchCoreRequest); // TODO: handle error
 
+  yield call(i18n.changeLanguage, user.language);
   yield call(i18n.loadCoreLocale);
 
   yield put(
@@ -48,3 +48,14 @@ export function* initializeCoreService() {
     ),
   );
 }
+
+export function* changeCoreLanguageService(language) {
+  if (language === null) {
+    yield call(i18n.detectLanguage);
+    yield call(i18n.loadCoreLocale);
+    yield call(i18n.changeLanguage, i18n.resolvedLanguage);
+  } else {
+    yield call(i18n.loadCoreLocale, language);
+    yield call(i18n.changeLanguage, language);
+  }
+}

client/src/sagas/core/services/user.js

@@ -1,6 +1,7 @@
 import { call, put, select } from 'redux-saga/effects';
 
 import { logoutService } from './login';
+import { changeCoreLanguageService } from './core';
 import request from '../request';
 import { currentUserIdSelector, currentUserSelector, pathSelector } from '../../../selectors';
 import {
@@ -81,6 +82,21 @@ export function* handleUserUpdateService(user) {
   yield put(handleUserUpdate(user, users, isCurrent));
 }
 
+// TODO: add loading state
+export function* updateUserLanguageService(id, language) {
+  yield call(changeCoreLanguageService, language);
+
+  yield call(updateUserService, id, {
+    language,
+  });
+}
+
+export function* updateCurrentUserLanguageService(language) {
+  const id = yield select(currentUserIdSelector);
+
+  yield call(updateUserLanguageService, id, language);
+}
+
 export function* updateUserEmailService(id, data) {
   yield put(updateUserEmail(id, data));