Allow videos in posts, simplify post image view

CHDataManagement/Model/Loading/LoadingContext.swift

@@ -79,6 +79,17 @@ final class LoadingContext {
         return nil
     }
 
+    func postMedia(_ imageId: String) -> FileResource? {
+        guard let image = file(imageId) else {
+            return nil
+        }
+        if image.type.isImage || image.type.isVideo {
+            return image
+        }
+        error("Post Media \(imageId) is not an image or video")
+        return nil
+    }
+
     func item(itemId: ItemId) -> Item? {
         switch itemId.type {
         case .post: