Feature / Dependency Update

## Background
As per the recently disclosed [CVE-2025-52893](https://nvd.nist.gov/vuln/detail/CVE-2025-52893), the [mitchellh/mapstructure](https://github.com/mitchellh/mapstructure) package has been identified as vulnerable. Security scanners are flagging this as a transitive dependency, which is triggering findings in our pipelines.

## Proposal
There is a maintained fork of the package under [go-viper/mapstructure](https://github.com/go-viper/mapstructure) that has already addressed this vulnerability. If the Consul team is open to it, I’d be happy to submit a PR replacing the current dependency with the patched fork.

Please let me know if this approach aligns with your standards and direction. I'm happy to assist with implementation.

No files or tests are identified in the issue. Start by locating the current mitchellh/mapstructure dependency in the Consul repository and compare the go-viper/mapstructure fork and its vulnerability fix. Done means the patched fork is adopted and dependency or security checks pass.

Written by the indexing model from the issue text.