Definitely. I use Gitlab CI/CD for my personal projects. 

I believe that it does. Not everything needs to be a Stimulus component. Sometimes it just makes sense to have some JS sprinkles where needed. I have personally never been a huge fan of page specific javascript as it seems like there is some disconnect in the architectural planning of the application. I typically tend to write JS functions so that they can be called on later in Server Rendered Javascript responses, when launching a bootstrap modal or wherever else appropriate.

Have a look at this episode to see if it covers your questions.

https://www.driftingruby.com/episodes/charts-and-graphs

You could use a UUID for this, but I think that it would probably be a bit overkill.

I would personally just do something like this with SecureRandom.hex (which is part of the ruby core)

        before_create :populate_subscriber_id
        private
        def populate_subscriber_id
          begin
            self.subscriber_id = SecureRandom.hex
          end while self.class.exists?(subscriber_id: subscriber_id)
        end

Since the difference was so minimal, it was probably something to do with the host environment. If it were X times slower, it would be a bit strange and cause for alarm, but I could have had a number of things running on the mac which created the slight differences.