DPL-381 Add links to issues in code where appropriate

[JamesGlover]

Describe the Housekeeping As a developer I would link to link github issues as todos comments in the codebase in order to make it easy to discover pending housekeeping changes. Eg.

# Create a new plate
# @todo This is using Time.now, whereas it should be using Time.current to avoid potential timezone issues
#             See https://github.com/sanger/sequencescape/issues/123
def broken_method
  Plate.create unless Time.now.tuesday?
end

Should be limited to issues that can easily be confined to a small chunk of code. Timebox it to a day at most to start.

Blocking issues Describe any other issues or tickets that may be blocking this change.

Additional context Add any other context about the problem here.