Fix opening attached documents

The file provider name needs to be all lower-case as it's used in the host
part of a URL. No idea how this worked previously.

src/app/android/AndroidManifest.xml

@@ -134,7 +134,7 @@
 
         <provider
             android:name="androidx.core.content.FileProvider"
-            android:authorities="org.kde.itinerary.documentProvider"
+            android:authorities="org.kde.itinerary.documentprovider"
             android:exported="false"
             android:grantUriPermissions="true">
             <meta-data

src/app/android/src/org/kde/itinerary/Activity.java

@@ -80,7 +80,7 @@ public class Activity extends QtActivity
     {
         Log.i(TAG, filePath);
         File file = new File(filePath);
-        return FileProvider.getUriForFile(this, "org.kde.itinerary.documentProvider", file);
+        return FileProvider.getUriForFile(this, "org.kde.itinerary.documentprovider", file);
     }
 
     /* Try to find attachment URLs from shared content from email applications.