Add 'last_updated' attribute to tables and cubes

[yannikbuhl]

Some users have pointed out that for automated data updates it would be helpful to have the date of last update to the data products such as table and cube. This could be easily achieved by adding the date of the last update as an attribute to the data object. In doing so, we could add further attributes to the objects, just like it is done in almost every other object generated by the package (e.g., Copyright, etc.).

[yannikbuhl]

Instead of adding this to the data objects, one could also use gen_metadata to check when an object was last updated.

Example:

check_object <- gen_metadata(code = "23131BJ020", database = "genesis", category = "cube")
attributes(check_object)$Updated

This will yield the date and time of the last update to the object, in this case a cube.