shibaken: switch outputted JSON keys from snake_case to kebab-case

[jpculp]

Issue number:

N/A

Description of changes:

This renames the snake_case in the Ssh struct to kebab-case when serializing the user data JSON.
This effectively replaces authorized_keys with authorized-keys which is more in line with Bottlerocket's current API standards.

This change is dependent on bottlerocket-os/bottlerocket-admin-container/pull/26

Testing done:

• Launched aws-ecs-1 instance.
• Instance connected to ecs cluster.
• Test task deployed successfully.
• Switched the admin container source to point to a patched admin container.
• Enabled and launched admin container.
• Connected to admin container via ssh.
• Verified that /.bottlerocket/host-containers/current/user-data contained the expected JSON:

{
   "ssh":{
      "authorized-keys":[
         "ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQClKsfkNkuSevGj3eYhCe53pcjqP3maAhDFcvBS7O6V
          hz2ItxCih+PnDSUaw+WNQn/mZphTk/a/gU8jEzoOWbkM4yxyb/wB96xbiFveSFJuOp/d6RJhJOI0iBXr
          lsLnBItntckiJ7FbtxJMXLvvwJryDUilBMTjYtwB+QhYXUMOzce5Pjz5/i8SeJtjnV3iAoG/cQk+0FzZ
          qaeJAAHco+CY/5WrUBkrHmFJr6HcXkvJdWPkYQS3xqC0+FmUZofz221CBt5IMucxXPkX4rWi+z7wB3Rb
          BQoQzd8v7yeb7OzlPnWOyN0qFU0XA246RA8QFYiCNYwI3f05p6KLxEXAMPLE my-key-pair"
      ]
   }
}

• Ran sudo sheltie to verify root shell was still available.
• Checked for failed systemd units.

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[zmrow]

🌃