i157: Add factory constructor to sub-problems

[T-Davis]

fixes #157

[T-Davis]

Fixes #157

[nickmeinhold]

Couple of quick adminny type comments:

• the PR titles should (imo) be quite short and snappy - the git history being easy to read is worth leaning toward brevity over clarity I reckon
  • I took the liberty of editing the title, please let me know if that was going too far :-)
• adding the "fixes #num" thing (I think) needs to be done in the main comment, ie. the first one, otherwise it doesn't link and close the issue
• as a reviewer it's super helpful to have the author point out anything unexpected or anything that will save you time - the reason it comes to mind is the formatter creating whole lot of changes in this case is an example where communicating there was something unexpected would be quite helpful
• anything that causes a lot of changes (like formatting, or renaming files, etc.) would ideally be done in a separate PR
  • we have an item in the CoC to this effect I believe, not sure if it covers formatting specifically though
  • personally I don't think it's worth pulling out the formatting into a separate PR at this point, just putting it out there for future PRs

Thanks again mate, awesome work!!!

[T-Davis]

@nickmeinhold Thanks for the feedback! Those are all great points, I'll pay more attention in the future. Sorry for the mess, next one will look good 👍

[nickmeinhold]

@T-Davis nothing to apologise for mate, bloody great work! 👍

[nickmeinhold]

Thanks @tamari-gray! I approved it already but wanted to check if you wanted to review as well. Looks like we're good to go!