add userMetadata option for dedicated server resource

[bigbigbang]

Description

To reflect APIV6 changes , we need to add the userMetadata option on dedicated server resource

Fixes #xx (issue)

Type of change

Please delete options that are not relevant.

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Improvement (improve existing resource(s) or datasource(s))
• [x] Documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

• [x] Test A: make testacc TESTARGS="-run TestAccDedicatedServerInstall_usermetadata"

Test Configuration:

• Terraform version: terraform version: Terraform 1.6.6
• Existing HCL configuration you used:

  resource ovh_dedicated_server_install_task "server_install" {
  service_name      = data.ovh_dedicated_server_boots.harddisk.service_name
  template_name     = ovh_me_installation_template.byolinux.template_name
  user_metadata     {
  image_url              = "https://github.com/ashmonger/akution_test/releases/download/0.6-fixCache/deb11k6.qcow2"
  image_type             = "qcow2"
  http_headers_0_key     = "Authorization"
  http_headers_0_value   = "Basic bG9naW46cGFzc3dvcmQ="
  image_checksum_type    = "sha512"
  image_checksum         = "047122c9ff4d2a69512212104b06c678f5a9cdb22b75467353613ff87ccd03b57b38967e56d810e61366f9d22d6bd39ac0addf4e00a4c6445112a2416af8f225"
  config_drive_user_data = "#cloud-config\nssh_authorized_keys:\n  - %s\n\nusers:\n  - name: aautret\n    sudo: ALL=(ALL) NOPASSWD:ALL\n    groups: users, sudo\n    shell: /bin/bash\n    lock_passwd: false\n    ssh_authorized_keys:\n      - %s\ndisable_root: false\npackages:\n  - vim\n  - tree\nfinal_message: The system is finally up, after $UPTIME seconds\n"
  }
  }

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings or issues
• [x] I have added acceptance tests that prove my fix is effective or that my feature works
• [x] New and existing acceptance tests pass locally with my changes
• [ ] I ran succesfully go mod vendor if I added or modify go.mod file

[bigbigbang]

need rework