Allow Office Excel to display and edit .xlsm files

Macro enabled excel files are not supported by Office Connector.
In fact, if we just rename the file from .xlsm to .xsl, the macro correctly displays it. And the Webdav work perfectly too. The only issue then is that Excel gives an unpleasant warning to the user.

The file preview is not so nice as the office macro. Because the advantage of the office macro is that users are strongly suggested to update the file inline instead of downloading it.
The file preview does not allow to preview, nor edit inline xlsm files.

The office macro allows also to embed the file in the page, having nice display.

This makes a big difference as usually when users start to download, they also go back to mails instead of keeping to confluence. They also start to rename files.

As it seams that it is just the extension name that causes troubles, could you add it to the acceptable list ?