chore(lint): configure goconst linter

[lexfrei]

What does it do?

Enables and configures the goconst linter in golangci-lint to detect repeated string literals that should be constants, while excluding well-known protocol values that don't benefit from being constants.

Motivation

Following up on the discussion started in #5889, this PR enables the goconst linter with appropriate configuration.

The linter is configured to catch genuinely problematic string repetitions (3+ occurrences) while avoiding noise from values that shouldn't become constants:

• DNS record types (A, AAAA, CNAME, TXT, etc.) - excluded as these are standard protocol values specific to DNS software and universally recognized
• Boolean strings ("true", "false") - actively used in several places throughout the codebase but not critical enough to warrant constants
• Common indicators ("none") - similar rationale to boolean strings
• Registry types (aws-sd, noop) - ideally these should be constants, but doing so would require rewriting the entire controller/execute.go package to use constants consistently for all provider and registry types, which would significantly reduce readability by mixing string literals and constants in switch statements

Setting min-occurrences: 3 ensures we catch project-specific strings that genuinely need constants while avoiding over-engineering for well-known values.

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests (N/A - configuration change only)
• Yes, I updated end user documentation accordingly (N/A - internal linting configuration)

[k8s-ci-robot]

Hi @lexfrei. Thanks for your PR.

I'm waiting for a github.com member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ivankatliarchuk]

/ok-to-test

[coveralls]

Pull Request Test Coverage Report for Build 18958949696

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 78.666%

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Totals
Change from base Build 18815330014:	0.0%
Covered Lines:	15863
Relevant Lines:	20165

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💛 - Coveralls

[ivankatliarchuk]

/lgtm

[mloiseleur]

thanks @lexfrei 👍

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mloiseleur

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