Add function to validate cidr superset

[jimmycgz]

SUMMARY

GCP doesn't allow to shrink of the CIDR of a subnet but the original module doesn't throw an error if the requested new CIDR is not a superset of the original IP range. This PR suggests adding a condition check and error out for this scenario.

Fixes #563

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

This PR suggests adding a condition check to error out the above-mentioned scenario, by comparing the requested new CIDR is not a superset of the original IP range of the subnet.

ADDITIONAL INFORMATION

GCP API will throw an error on this case which the current ansible module doesn't handle. Refer the API guide for details. https://cloud.google.com/compute/docs/reference/rest/v1/subnetworks/insert

After this suggested change, A fatal error will occur to handle the above-mentioned case. Which tells the user to extend the CIDR instead of shrinking, eg: from 10.10.0.0/20 to 10.10.0.0/18 (Correct) or 10.10.0.0/22 (Incorrect) or 172.16.0.0/18(Incorrect).

[toumorokoshi]

This looks good to me, and I ran integration tests locally so safe to merge

Is there a way we can / should test this in an automated fashion? Wanted to ask in case we can verify this behavior via CI in the future before I merge.

[toumorokoshi]

nit: i'd suggest something like result_is_superset to indicate that the value is a boolean (It's hard to infer the type of result_superset).

[jimmycgz]

Thanks @toumorokoshi for the suggestion, I changed it to result_is_superset.

[toumorokoshi]

actually looks like lint failed. Can you fix your styling and ensure integration tests pass before I merge?