feat(report): added Gitlab SAST report

[felipe-avelar]

Closes #1986

Proposed Changes

• Added a new report format glsast, which will generate a file to be used with Gitlab SAST integration

I submit this contribution under the Apache-2.0 license.

[kicsbot]

Scan submitted to Checkmarx

[kicsbot]

Checkmarx SAST - Scan Summary & Details

Cx-SAST Summary

Total of 0 vulnerabilities
 0 High
 0 Medium
 0 Low
 0 Info

Violation Summary

No policy violation found

[joaoReigota1]

LGTM

[rogeriopeixotocx]

LGTM

[theoretick]

Hi all, Gitlabber here! This is really exciting to see shipped!

Apologies for missing this earlier but we just noticed a couple minor issues here I wanted to follow-up on:

1. Our category field is actually an enum of the report type. This is used internally for grouping the reports correctly and should be sast here. I realize this was an issue with our schema and not well documented. Sorry about that! We just opened https://gitlab.com/gitlab-org/gitlab/-/issues/332054 to track this one.
2. Our severity field is also an enum and should be camelcase; i.e. High not high.

We are also working on deploying a more accessible schema validator to make these integrations more straightforward. It didn't pick up on the first issue but the second is validated correctly. You can currently find it at https://gitlab-org-security-products-secure-schema-validator.34.127.22.151.sslip.io/ until we spin up a more permanent domain.

I opened a follow-up PR here to address these two items: #3460.