Add a `description` entry to job definition in CI configuration
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### Release notes
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## Problem
A job name is usually a short string that rarely describes a purpose of the CI job adequately.
### Intended users
* [Sasha (Software Developer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#sasha-software-developer)
* [Devon (DevOps Engineer)](https://about.gitlab.com/handbook/marketing/product-marketing/roles-personas/#devon-devops-engineer)
## Proposal
Add `description` keyword to a job definition in `.gitlab-ci.yml`.
**NOTE:** We will start with a 128 character limit for `description` and then adjust as we go in the future.
```yaml
rspec:
script: rspec
description: 'Unit tests for GitLab'
rubocop:
script: rubocop
description: 'Static code analysis'
```
If the description is present, show it the job detail page.
| Job detail page. |
| ------ |
|  |
- The job detail page can show the full description.
### Permissions and Security
Anyone who can create a CI YAML config will be able to add the `description` keyword to a job. Anyone who can see the pipeline graph will be able to see the tooltip description. Those users who can see the job detail page will see the description in the job page.
<!-- What permissions are required to perform the described actions? Are they consistent with the existing permissions as documented for users, groups, and projects as appropriate? Is the proposed behavior consistent between the UI, API, and other access methods (e.g. email replies)?
Consider adding checkboxes and expectations of users with certain levels of membership https://docs.gitlab.com/ee/user/permissions.html
* [ ] Add expected impact to members with no access (0)
* [ ] Add expected impact to Guest (10) members
* [ ] Add expected impact to Reporter (20) members
* [ ] Add expected impact to Developer (30) members
* [ ] Add expected impact to Maintainer (40) members
* [ ] Add expected impact to Owner (50) members -->
### Documentation
The new keyword needs to be documented in the keyword reference as well as the jobs documentation.
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### Availability & Testing
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What risks does this change pose to our availability? How might it affect the quality of the product? What additional test coverage or changes to tests will be needed? Will it require cross-browser testing?
Please list the test areas (unit, integration and end-to-end) that needs to be added or updated to ensure that this feature will work as intended. Please use the list below as guidance.
* Unit test changes
* Integration test changes
* End-to-end test change
See the test engineering planning process and reach out to your counterpart Software Engineer in Test for assistance: https://about.gitlab.com/handbook/engineering/quality/test-engineering/#test-planning -->
### Available Tier
* Free
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* Free
* Premium/Silver
* Ultimate/Gold
-->
### Links / references
- [UX research insight](https://dovetailapp.com/projects/b3af4fd0-21f6-42fe-b092-6ec2d37cdd43/insights/present/ee2cb253-30bf-476a-925f-e0f72d0bb9c2)
- https://gitlab.slack.com/archives/questions/p1479474951004415
/cc @ayufan @markpundsack @selfup @cperessini
issue