Several instance mutation views crashed with a bare HTTP 500 when a form field
the UI always sends was absent or malformed (a direct or crafted request);
ExceptionMiddleware turns only libvirt and timeout errors into 4xx, so these
reached a 500. Fixed:
- add_network parsed a None network source ("'NoneType' has no attribute
'split'"); it now requires a selected network.
- set_qos read an unbound local 'mac' when no field name contained "mac", and
passed an invalid direction or non-numeric rate to the proxy (ValueError); it
now requires a MAC, an inbound/outbound direction and whole-number rates.
- unset_qos passed an empty direction into the proxy's XPath (XPathEvalError);
it now requires a MAC and a valid direction.
- resizevm_cpu and resize_memory ran int() over an empty or non-numeric value;
they now validate with int() (not str.isdigit(), which accepts "²" that
int() rejects).
- add_public_key passed a missing/non-numeric sshkeyid into an integer-id
lookup (ValueError); it now requires a numeric id.
Each reports the problem and returns to the VM page without calling libvirt or
logging, as change_network already does.
Tests: each view with a field missing, non-numeric or a unicode digit returns
302 with an error message, writes no log, and does not attempt the mutation.
The tests fail on the previous code.
