Allow Code Lenses without a command

[andyw8]

Motivation

For Shopify/ruby-lsp-rails#241, I'd like to ship a first iteration which shows the Code Lens but doesn't have any associated command.

Implementation

Allow command_name to be nil.

Automated Tests

n/a

Manual Tests

• Check out https://github.com/Shopify/ruby-lsp-rails/pull/lookup_route (the Gemfile is temporarily pointing to this branch)
• Open test/dummy/app/controllers/users_controller.rb
• Ensure the Code Lenses appear above each action
• Ensure clicking the Code Lens has no affect

[vinistock]

I don't think we should allow this. When a code lens has no command, the spec mentions it will be an unresolved code lens, meaning that a codeLens/resolve request will be sent when the user clicks on it.

Why do we want to ship a code lens with no command associated to it? Why not ship the complete implementation?