feat!(v2): csv - validate license URL and guess more if invalid

[Bobgy]

Fixes #73

Assumption: the license URL we want to collect is always publically accessible
If there are concerns with this assumption, we can discuss several options:

• hide the feature under a flag
• enable validation by default, but provide a flag to disable this feature. Note we will be releasing v2, so we can consider making a breaking change if that's the default behavior we prefer.

[gwatts]

@Bobgy any thoughts on updating this and merging? i have a project that is being tripped up by this issue; i think this is a reasonable approach to solve it

[gwatts]

opened #328 as an alternative option to this pr that avoids using the network to check if the url is reachable