Improve FOSSA integration

[yurishkuro]

Related to FOSSA scanning introduced in #2347

• make the check go red when license violations are discovered
• make the scan report easily accessible, e.g. by clicking on the Details next to the check, and/or posting a summary as a PR comment

[idvoretskyi]

@yurishkuro happy to address this:

make the check go red when license violations are discovered

It's so easy as adding an extra line to the configuration - f136083#diff-3e1f48f43ea04daf7c61b8915f2d1d94R28, but as we've discovered recently - FOSSA scan can take a huge amount of time and fail for some reason. Also, it may happen that FOSSA scan can find some licensing "issues" which are not the real issues, but the incorrect interpretation by their engine (we've discussed that with you, Yuri, via email), which were reported as bugs to FOSSA.

So I can add this easily, but we may want to revert this behavior back.

make the scan report easily accessible, e.g. by clicking on the Details next to the check, and/or posting a summary as a PR comment

Posting a summary as a PR comment is not possible, unfortunately (I've raised this up to FOSSA already). I'll investigate if we can make access to the reports easier.

The first thing that comes to my mind - adding a badge to the project README file: https://docs.fossa.com/docs/quick-import#getting-a-badge-pull-request-githubcom-only

[idvoretskyi]

@yurishkuro I've noticed that you already have a FOSSA badge in the README, so updated a link here - #2446