Generate instrumentation files with custom metric definition generator

We introduced the Usage Ping instrumentation files !57333 (closed)

It would be helpful to have this 2 files with a basic structure generated by the custom generator https://gitlab.com/gitlab-org/gitlab/-/blob/master/lib/generators/gitlab/usage_metric_definition_generator.rb

• <metric>_metric.rb
• <metric>_metric_spec.rb
• Files should have the name with _metric suffix
• Basic structure

# `<metric>_metric.rb`
# frozen_string_literal: true

module Gitlab
  module Usage
    module Metrics
      module Instrumentations
        class <MetricName>Metric < <RedisHLL|Generic|Database>Metric
          def value

          end
        end
      end
    end
  end
end

# `<metric>_metric_spec`.rb
# frozen_string_literal: true

require 'spec_helper'

RSpec.describe Gitlab::Usage::Metrics::Instrumentations::<MetricName>Metric do
  it_behaves_like 'a correct instrumented metric value', <expected value>
end

Proposal

bundle exec rails generate gitlab:usage_metric --type=database

Where type can be database, redis_hll, generic

Should have --ee option for metrics available under ee. In this case metrics should be created under ee/lib/gitlab/usage/metrics/instrumentations/