Special chars are not supported in the agent registration command although they can be used in ssh

The use of any special chars in the tags of the opentf-agent command does not work while it works correctly with ssh.

For example, the following command:

opentf-agent --name "agent-cucumber1" --token $TOKEN --namespaces projet3 --tags projet_3,cucumber,cucumber5,linux,junit --host $HOST --port 24368

diplays the following error:

When using SSH, the tags can contain any special chars without causing any error.

To conclude:

1. The behavior is not iso-functional between ssh and agent
2. The error displayed in the log is not explicit
3. If we decide not to support the underscore, we should add it in the doc

From issue SQSUP-4164