Change activity log to track all changes made to the dataset IN DETAIL

[lauradryad]

Problem description, and links to relevant helpdesk tickets:
Currently, the activity log only captures the high level status changes that occur in a dataset, but not what was changed within the dataset on each version. While the Review page does highlight the changes, this requires curators to edit a dataset in order to find out what changed. In addition, this feature will assist when we allow multiple collaborators in a dataset so they can see what each other has changed.

Describe the solution you'd like:
We would like for the activity log to capture the specific details of what is changed within a dataset instead of relying on the author to describe their changes. I'm not sure what detail one is able to capture at this level, but at least marking which sections were altered or files changed would be helpful.

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Note for Alin from Audrey
Currently we have 2 different tables with notes for changes—curation activities and edit histories. The edit histories seemingly only records notes users leave when editing a dataset. Most other notes are recorded in curation activities—I think they were put there only because that is what the curators see in the activity log. This makes things complicated, because the primary purpose of curation activities is to track status changes, but now it's chock full of random notes as well.

I suggest you:

1. Change the curation activities log to ONLY track status changes & new versions. Move all non-status-changing notes to the edit histories table.
2. Record all changes to a dataset or its metadata somewhere (using one of these gems you've suggested?)

Then we can expose all 3 of these things—status & version logs, curator and user notes, and actual change tracking—in the activity log UI on demand

[ahamelers]

This ticket should be for handling creating the detailed logs in the database (Alin has suggested several gems)

I will handle the front end afterward in #3534