model: Add resolved copyright source

[porsche-rbieniek]

This pull request adds an additional property to the resolved copyright finding to let reporter implementations know where a copyright statement originates from.

We have an use case in our reporter implementations where the output of a copyright statement is allowed only if

• the copyright statement is provided by a curation
• the copyright statement is determined by the scanner

This change introduces a clear-cut property which allows reporter implementations to decide on a exact condition.

This pull request is blocked by #5504