Make notifications spoiler aware

[OpaqueReptile]

An attempt to implement matrix-org/matrix-spec-proposals#3124, and address #3477

Signed-off-by: Preston Frazier @preston:inferiorlattice.com

Pull Request Checklist

• Changes has been tested on an Android device or Android emulator with API 21
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request includes a new file under ./changelog.d. See https://github.com/vector-im/element-android/blob/develop/CONTRIBUTING.md#changelog
• Pull request includes screenshots or videos if containing UI changes
• Pull request includes a sign off
• You've made a self review of your PR
• If you have modified the screen flow, or added new screens to the application, you have updated the test UiAllScreensSanityTest.allScreensTest()

[bmarty]

Hello @paftree, thanks for the PR.
Can you add a screenshot of a notification with a spoiler to demo your change?

[OpaqueReptile]

Added more screenshots above.

[ouchadam]

for my own understanding, does this change only hide spoilers in the direct message/room list and notifications? (all the places that use getLastMessageBody)

The spoilers will still be visible within the message timeline?

[OpaqueReptile]

Right, the current behavior is using the unformatted message body in the room list/notifications where most clients will just put the spoiler verbatim... which somewhat defeats the point of having spoiler text at all.

This change attempts to replace any spoiler text with fullblock characters in non-html-formatted places. The actual message in the room will still be hidden/viewable by the data-mx-spoiler attribute.

[bmarty]

Merge on one of my branch, will create a new PR soon