Video playback (#308)

* Create media player screen

* Introduce `FileCache` to cache message attachments

* Add file loading functionality into the media provider

* Process tap action on timeline items

* Pass item taps to view model

* Navigate to media player on view model callback

* Commit project file

* Add changelog

* Rename media to video

* Add a loader when large videos being processed

* Add back button explicitly on video screen, fixes for light scheme

* Handle right swipe to dismiss video

UnitTests/Sources/VideoPlayerViewModelTests.swift

@@ -0,0 +1,44 @@
+//
+// Copyright 2022 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import XCTest
+
+@testable import ElementX
+
+@MainActor
+class VideoPlayerScreenViewModelTests: XCTestCase {
+    var viewModel: VideoPlayerViewModelProtocol!
+    var context: VideoPlayerViewModelType.Context!
+    
+    @MainActor override func setUpWithError() throws {
+        viewModel = VideoPlayerViewModel(videoURL: URL(staticString: "https://storage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"), autoplay: true)
+        context = viewModel.context
+    }
+
+    @MainActor func testCancel() async throws {
+        var correctResult = false
+        viewModel.callback = { result in
+            switch result {
+            case .cancel:
+                correctResult = true
+            }
+        }
+
+        context.send(viewAction: .cancel)
+        await Task.yield()
+        XCTAssert(correctResult)
+    }
+}