Add support for creation of NB with IPv4 Reserved Address

[hcwagner]

📝 Description

This adds support for creating a NodeBalancer with a reserved IP address. It will be supported by an upcoming release to modify Linode API to accept reserved IPs at the creation of a NodeBalancer. This is needed to support the creation of Service LoadBalancers with reserved IPs in LKE.

✔️ How to Test

Customer flags required:

• reserved_ips_beta
• can_reserve_ip
• reserved_ip_nodebalancer

Relevant unit tests can be run using:

make TEST_ARGS="-run TestNodeBalancer" test-unit

Relevant files:

• test/unit/fixtures/nodebalancer_create_with_ipv4.json
• test/unit/nodebalancer_test.go

[jriddle-linode]

Code looks good, pending test environment for release.

[ezilber-akamai]

Looks good! Thank for for the contribution. Will approve after testing.

[hcwagner]

Just an update for those watching. The production updates to the Linode API required to support this are currently scheduled for next week (9/14 and 9/16). I'll update the PR once they are successfully rolled out.