Merge branch 'regression/cron_jobs_validation' into 'master'

Log cron_jobs configuration instead of raising exception

## What does this MR do?

Log cron_jobs configuration errors and remove invalid key <-> values from the configuration hash instead of raising an exception.
This has been discussed at #20010.

Fixes #20010

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

Original implementation !5318, introduced a regression with our docker packaging: #20010.

## What are the relevant issue numbers?

* #20010 
* #18378

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5360

CHANGELOG

@@ -126,7 +126,7 @@ v 8.10.0 (unreleased)
   - Fix last update timestamp on issues not preserved on gitlab.com and project imports
   - Fix issues importing projects from EE to CE
   - Fix creating group with space in group path
-  - Improve cron_jobs loading error messages !5318
+  - Improve cron_jobs loading error messages !5318 / !5360
   - Create Todos for Issue author when assign or mention himself (Katarzyna Kobierska)
   - Limit the number of retries on error to 3 for exporting projects
   - Allow empty repositories on project import/export

config/initializers/sidekiq.rb

@@ -18,7 +18,8 @@ Sidekiq.configure_server do |config|
     if cron_jobs[k] && cron_jobs_required_keys.all? { |s| cron_jobs[k].key?(s) }
       cron_jobs[k]['class'] = cron_jobs[k].delete('job_class')
     else
-      raise("Invalid cron_jobs config key: '#{k}'. Check your gitlab config file.")
+      cron_jobs.delete(k)
+      Rails.logger.error("Invalid cron_jobs config key: '#{k}'. Check your gitlab config file.")
     end
   end
   Sidekiq::Cron::Job.load_from_hash! cron_jobs