Fix Duplicate Keys in Vulnerability Details

What does this MR do?

On the vulnerability details page, if two identifiers have the same URL, it will log an error message in the console. That's because the unique key is set to the URL and won't be unique if two identical URLs are used. This MR fixes that behavior by computing the key using a combination of the index and URL.

Relates to #247045 (closed).

Screenshots

Before

After

Steps to test

To test the changes, you need a vulnerability with at least two identifiers that have the same URL. You can either create them through a pipeline or through the rails console. Alternatively, if you are lazy—like me—you can add this to the component definition 🙈

created() {
  this.vulnerability.identifiers = [
    {
      url: 'https://gitlab.com',
      name: 'CVE-2019-9169 (1st)',
    },
    {
      url: 'https://gitlab.com',
      name: 'CVE-2019-9169 (2nd)',
    },
    {
      url: 'https://about.gitlab.com',
      name: 'different URL',
    },
  ];
},

When you create the identifier, you could also use an actual URL but I replaced it for readability (and because it's caused by a specific URL): https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-9169

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