Add support for meta block in vercel_deployment

[polo4096]

Currently, the vercel_deployment resource does not support a meta block to attach metadata to deployments. In the Vercel CLI, the --meta flag allows users to include metadata with their deployments, which is beneficial for tracking and managing deployments effectively. ​

Proposal:

Introduce a meta block within the vercel_deployment resource to allow users to specify metadata key-value pairs. This enhancement would align the Terraform provider's capabilities with those of the Vercel CLI, providing a consistent experience across deployment methods.​

Example:

resource "vercel_deployment" "example" {
  project_id = var.project_id
  files       = data.vercel_prebuilt_project.example.output
  path_prefix = data.vercel_prebuilt_project.example.path
  meta = {
    githubCommitRef        = var.github_commit_ref
    githubCommitAuthorName = var.github_commit_author_name
    githubCommitMessage    = var.github_commit_message
  }
}

Benefits:

• Enhanced deployment tracking and management by associating custom metadata.​
• Consistency between Vercel CLI and Terraform provider functionalities.​
• Improved automation capabilities in CI/CD pipelines.

See https://vercel.com/docs/cli/deploy#meta