Draft: Usage ping declarative syntax POC

What does this MR do?

This MR is a POC of an idea for &3903 (closed).

• Each metric is calculated in a separate sidekiq job

• Metric jobs write their resulting data to redis

• A cron job periodically checks to see of all metric jobs are finished

• If all are finished, it will gather the data from redis and submit usage ping

• This cron job can use a waitgroup-like pattern to know if all metric jobs are finished

Unknowns

• How do we limit concurrency of jobs, to prevent overwhelming the DB?
• How can the metric jobs share min/max ID?
  • Cache them in redis?

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team