Allow modifying scaling groups in the modify_keypair mutation

[ironAiken2]

Main idea

teams

Currently, to set a scaling_group for a keypair, we need to use the associate_scaling_groups_with_keypair mutation in addition to the modify_keypair mutation. This can have unexpected side effects and is not a good practice in terms of error handling.

To address these issues, it is proposed to modify the modify_keypair mutation to include the ability to modify scaling_groups. This change will streamline the process and improve the overall functionality and reliability of the system.

Anything else?

Currently, if scaling_groups are assigned to the Keypair, it cannot be reassigned to 'associate_scaling_groups_with_keypair' mutation. For reassignment, we must deallocate through 'disassociate_scaling_groups_with_keypair' mutation and try again with 'associate_scaling_groups_with_keypair' mutation.

And neither both association nor disassociation mutations work with scaling_groups argument of empty strings or empty arrays.