Intent to Deprecate HCLv1

[schmichael]

Nomad adopted HCLv2 for Jobspecs in 2020. HCLv2 is not strictly backward compatible with HCLv1, so we have maintained the HCLv1 jobspec parser behind the nomad job run -hcl1 ... flag, the job parse HCLv1 field, and the jobspec Go package.

Deprecation Plan

The time has come to deprecate HCLv1.

• After Nomad 1.8.0 no new jobspsec fields will be added to the jobspec package.
• In Nomad 1.9.0 all hclv1 support will be removed.

TODO

• [ ] Add deprecation warning to CLI in Nomad 1.8.0
• [ ] Add deprecation comments to jobspec package in Nomad 1.8.0
• [ ] Add deprecation notes to docs
• [ ] Create a followup issue for total removal in Nomad 1.9.0

Resources

• Original HCLv2 issue: #7220