In the sar-c_safe reader, add platform_name to the attribute.

[TAlonglong]

I would like to have the platform_name in the attributes in this reader.

The filename_info has the mission_id. This can be translated to platform_name like:

In the init of the SAFGRD:
self._mission_id = filename_info['mission_id']

and in get_dataset something like:
data.attrs.update({'platform_name': self._mission_id})

[mraspaud]

Good idea! PR welcome :)