chore(lint): use Go stdlib variables for HTTP methods and status codes

[thevilledev]

What

• Modify net/http related calls to consistently use HTTP methods and response codes from variables/constants provided by the pkg.
• Add usestdlibvars to lint configuration.

See #18061 and #18062 for changes related to node pool and variable endpoints.

Why

Some parts of the codebase already use these. With this PR, better code consistency and reliability.

[jrasell]

Hi @thevilledev and thanks so much for this PR, it LGTM.

Before merging I wanted to ask whether it would be possible to split this up slightly into 3 separate PR's, which would help backporting. Ideally the PR's would address the following areas, so I can backport to different release branches:

• node pools
• variables
• everything else

Being particular about backporting will make future development and backporting easier.

[thevilledev]

Happy to help and thank you for the review @jrasell!

In terms of backporting, I can definitely split this into three separate PRs. Just to confirm, would this splitting work?

• PR1: Node pools (node_pool_endpoint.go and node_pool_endpoint_test.go)
• PR2: Variables (variable_endpoint.go and variable_endpoint_test.go)
• PR3: Everything else

[jrasell]

Happy to help and thank you for the review @jrasell!

In terms of backporting, I can definitely split this into three separate PRs. Just to confirm, would this splitting work?

• PR1: Node pools (node_pool_endpoint.go and node_pool_endpoint_test.go)
• PR2: Variables (variable_endpoint.go and variable_endpoint_test.go)
• PR3: Everything else

Exactly; thanks again @thevilledev!

[thevilledev]

Alright, all done! I removed those two changes from this PR so please consider this as the third PR consisting of changes for the rest of the files and linting 👍