Add embargo_history to embargo removal.

[weiweishi]

Is your feature request related to a problem? Please describe.
For auditing purpose, we'd like to keep a history for embargoes. We have implemented embargo_history in the data model, and have migrated the data. We should keep the embargo history for any change to embargo through the background job, or through the UI.

Describe the solution you'd like
embargo_history is an array of strings.
We can construct the text as such:
"An embargo was deactivated on DateTime_when_embargo_was_lifted. Its release date was embargo_date. Intended visibility after embargo was visibility_after_embargo"
This can apply for both elapsed embargoes lifted through the background job, as well as any modification done through the UI.

[weiweishi]

Check with @leahvanderjagt to see how we should capture when the embargo is activated.
suggested text:
"An embargo was activated on DateTime_when_embargo_was_activated. Its release date will be embargo_date. Intended visibility after embargo will be visibility_after_embargo".
And what to do at the time of item deposit.
This will be a separate discussion with @leahvanderjagt and will be captured in a different issue.