compose: Do try to save photos to device camera roll, after all

In 2c2141b, we stopped passing `saveToPhotos: true` to
launchCamera, since it seemed unnecessary, and also awkward to have
to request storage permissions.

But Greg found that it's quite normal for apps with messaging to
save photos to storage when capturing from the camera [1] [2].

We also found that Android's "scoped storage" feature, which we've
enabled on Android 10+, means that this won't come with the extra
storage-permission request on Android 10+.

We do need a permissions check for Android 9 and below, though. And
since the react-native-image-picker upgrade in 36d3644, that
package hasn't been doing that permissions check for us. So we have
to do it ourselves; we reuse androidEnsureStoragePermission from
src/lightbox/download.js for that. For what this UI looks like, see
  https://chat.zulip.org/#narrow/stream/48-mobile/topic/saving.20photos.20to.20device.20on.20capture/near/1271686.

It will also mean a permission check on iOS, regardless of iOS
version; but again, other apps are doing this.

So, bring back `saveToPhotos: true`.

[1] https://chat.zulip.org/#narrow/stream/48-mobile/topic/saving.20photos.20to.20device.20on.20capture/near/1271585
[2] https://chat.zulip.org/#narrow/stream/48-mobile/topic/saving.20photos.20to.20device.20on.20capture/near/1271597

src/compose/ComposeMenu.js

@@ -21,6 +21,7 @@ import {
 } from '../common/Icons';
 import AnimatedComponent from '../animation/AnimatedComponent';
 import { uploadFile } from '../actions';
+import { androidEnsureStoragePermission } from '../lightbox/download';
 
 type OuterProps = $ReadOnly<{|
   expanded: boolean,
@@ -134,10 +135,33 @@ class ComposeMenuInner extends PureComponent<Props> {
     );
   };
 
-  handleCameraCapture = () => {
+  handleCameraCapture = async () => {
+    const _ = this.context;
+
+    if (Platform.OS === 'android') {
+      // On Android ≤9, in order to save the captured photo to storage, we
+      // have to put up a scary permission request. We don't have to do that
+      // when using "scoped storage", which we do on later Android versions.
+      await androidEnsureStoragePermission({
+        title: _('Storage permission needed'),
+        message: _(
+          'Zulip will save a copy of your photo on your device. To do so, Zulip will need permission to store files on your device.',
+        ),
+      });
+    }
+
     launchCamera(
       {
         mediaType: 'photo',
+
+        // On Android ≤9 (see above) and on iOS, this means putting up a
+        // scary permission request. Shrug, because other apps seem to save
+        // to storage, and it seems convenient; see
+        //   https://chat.zulip.org/#narrow/stream/48-mobile/topic/saving.20photos.20to.20device.20on.20capture/near/1271633.
+        // TODO: Still allow capturing and sending the photo, just without
+        // saving to storage, if storage permission is denied.
+        saveToPhotos: true,
+
         includeBase64: false,
       },
       this.handleImagePickerResponse,

static/translations/messages_en.json

@@ -1,5 +1,7 @@
 {
   "Error": "Error",
+  "Storage permission needed": "Storage permission needed",
+  "Zulip will save a copy of your photo on your device. To do so, Zulip will need permission to store files on your device.": "Zulip will save a copy of your photo on your device. To do so, Zulip will need permission to store files on your device.",
   "Something went wrong, and your message was not sent.": "Something went wrong, and your message was not sent.",
   "Message not sent": "Message not sent",
   "Please specify a topic.": "Please specify a topic.",