Provide an endpoint for logging CSP violations

[php-coder]

In order to be notified about Content Security Policy violations, we need to have an endpoint which just prints the report to the log.

Here is an example of such a report (but it's just for information): https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP#Sample_violation_report

Requirements:

• add new controller (CspController) in ru.mystamps.web.feature.site package
• add the endpoint that accepts POST requests on /site/csp/reports and outputs the request body to log

Part of #226

[php-coder]

@MainStar Hi, let me know if you need a help.

[MainStar]

Hi, yes sure, I just need some time, cuz now I am in vacation, and then I will relocate to another city, and I will need to organize it.

[php-coder]

@MainStar Ok, thanks for the information! Ping me when the dust will settle down :)

[MainStar]

Yes, sure :)

[php-coder]

@MainStar I'm sorry but as I want to push this task forward, I had to re-assign it from you.

[MainStar]

Hi, Ok, no problem.