Feat: Add `PaperTrail` to MVP to enable `item.text` History!

[nelsonic]

The outcome of our PaperTrail learning [SPIKE] was successful: https://github.com/dwyl/phoenix-papertrail-demo We need to outline how we are going to apply it to the MVP so that we can capture versions of item.text so that there is a full history of the changes made to the item. 👍

Todo

@LuchoTurtle given that you have the most knowledge in the team of this, please:

• [x] Outline how the DB Table Schema will change following the introduction of PaperTrail [please comment below!]
• [x] Document all the steps to add PaperTrail in buildit.md, but link to the dwyl/phoenix-papertrail-demo for the "boilerplate" parts.
• [x] Implement it with tests.
• [ ] Showcase it tomorrow at standup. 😉

Don't worry, not asking you to implement the UI/UX for this, yet ... just the backend! 👌

[LuchoTurtle]

With the introduction of Papertrail, the DB won't suffer many changes: only one table is going to be added to track item changes. So the items, items_tags, people, tags and timers table won't suffer any changes.

A new table will be introduced instead: versions (we perhaps we could change it to changes or something you find more idiomatic). This table will be used to track changes to the items table (for now) but can be extended for other tables as well. It will reference the people table to track who made the change.

[nelsonic]

versions is fine as the table name. We can change it later if needed. 👍 (thanks!)