Add ability to detect calendar permission description in the plist file (iOS)

ios/sdk/src/AppInfo.m

 - (NSDictionary *)constantsToExport {
     NSDictionary<NSString *, id> *infoDictionary
         = [[NSBundle mainBundle] infoDictionary];
+
+    // calendarEnabled
+    BOOL calendarEnabled
+        = infoDictionary[@"NSCalendarsUsageDescription"] != nil;
+
+    // name
     NSString *name = infoDictionary[@"CFBundleDisplayName"];
-    NSString *version = infoDictionary[@"CFBundleShortVersionString"];
 
     if (name == nil) {
         name = infoDictionary[@"CFBundleName"];
             name = @"";
         }
     }
+
+    // sdkBundlePath
+    NSString *sdkBundlePath = [[NSBundle bundleForClass:self.class] bundlePath];
+
+    // version
+    NSString *version = infoDictionary[@"CFBundleShortVersionString"];
+
     if (version == nil) {
         version = infoDictionary[@"CFBundleVersion"];
         if (version == nil) {
         }
     }
 
-    NSString *sdkBundlePath = [[NSBundle bundleForClass:self.class] bundlePath];
-
     return @{
+        @"calendarEnabled": [NSNumber numberWithBool:calendarEnabled],
         @"name": name,
         @"sdkBundlePath": sdkBundlePath,
         @"version": version

react/features/app/functions.native.js

-/* @flow */
+// @flow
+
 import { NativeModules } from 'react-native';
 
 export * from './getRouteToRender';

react/features/calendar-sync/middleware.js

 // @flow
 
+import { NativeModules } from 'react-native';
 import RNCalendarEvents from 'react-native-calendar-events';
 
 import { APP_WILL_MOUNT } from '../app';
         { dispatch, getState },
         maybePromptForPermission,
         forcePermission) {
+    if (!_isCalendarEnabled()) {
+        // The calendar feature is not enabled.
+        return;
+    }
+
     const state = getState()['features/calendar-sync'];
     const promptForPermission
         = (maybePromptForPermission && !state.authorization)
     return null;
 }
 
+/**
+ * Determines whether the calendar feature is enabled by the app. For
+ * example, Apple through its App Store requires NSCalendarsUsageDescription in
+ * the app's Info.plist or App Store rejects the app.
+ *
+ * @returns {boolean} If the app has enabled the calendar feature, {@code true};
+ * otherwise, {@code false}.
+ */
+export function _isCalendarEnabled() {
+    const { calendarEnabled } = NativeModules.AppInfo;
+
+    return typeof calendarEnabled === 'undefined' ? true : calendarEnabled;
+}
+
 /**
  * Retreives the domain name of a room upon join and stores it in the known
  * domain list, if not present yet.