fix: capture all fields of WorkspaceOwner when converting to cty.Value

[aslilac]

...so that terraform has access to all of the fields that it's supposed to!

[Emyrk]

We might want to add something like this:

	if o.Groups == nil {
		o.Groups = make([]string, 0)
	}
	
	if o.RBACRoles == nil {
		o.RBACRoles = make([]WorkspaceOwnerRBACRole, 0)
	}

nil vs empty slice might behave differently when actually using the type in terraform.

[aslilac]

I already allocate a slice regardless of length for the roles. poking at the resulting object did reveal that not allocating a slice for groups causes problems, so I do that now as well.