Add sast-scanner

[nabadger]

See:

• https://docs.gitlab.com/ee/user/application_security/sast/index.html#overview
• https://gitlab.com/mintel/appsec/sastconvertor/

We're starting to integrate SAST into gitlab-ci pipelines, but we should also be able to run locally too.

[charlieparkes]

This would be great! Is it converting a gitlab specific report or is it generated by a specific tool we could run ourselves too?

[nabadger]

We can run the tool - it will just analyze the code and generate a JUnit XML output report - probably would work with the Jenkins JUnit Plugin too!

Example XML: https://gitlab.com/mintel/appsec/sastconvertor/-/blob/master/testdata/out-report-2.xml