Scan external pull requests with sonarcloud

[Sander3003]

User Story

Allow scanning external pull-requests with Sonarcloud.

Acceptance criteria
Find a way to scan external pull-requests in CoMPAS.
Keep the traceability to the original author

Background:
@apupier

"I noticed one place missing the environment variable which is for the upload of Sonar analysis.
I found the feature request on Sonar side https://portal.productboard.com/sonarsource/1-sonarcloud/c/50-sonarcloud-analyzes-external-pull-request
And a slightly complicated workaround description: https://community.sonarsource.com/t/how-to-use-sonarcloud-with-a-forked-repository-on-github/7363/34"

[Sander3003]

Please add some documentation in order to keep this knowledge for further repositories. You can also make a proposal where to add the this fix. Suggestion, add it to all current CoMPAS project repositories with Sonarcloud enabled: https://sonarcloud.io/organizations/com-pas/projects