Improper protection of FileContentProvider

Some data in the FileContentProvider is protected against applications not related to NextCloud. The application checks if calling application package name contains "com.nextcloud.client" string. Every application with such substring in package name is allowed to fully access FileContentProvider.

    private boolean isCallerNotAllowed() {
        String callingPackage = this.mContext.getPackageManager().getNameForUid(Binder.getCallingUid());
        return callingPackage == null || !callingPackage.contains(this.mContext.getPackageName());
    }