feat: ✨ add calendar scraper and dump endpoint

[ecxyzzy]

Summary

• Add automated scraper for the calendar endpoint, which will run every three months (probably on the generous side but you never know).
• Calling /v1/rest/calendar with no params will now dump all terms in the database. The GraphQL query allTermDates accomplishes the same.
• Add the field socAvailable to the response type, which indicates when the Schedule of Classes will become available for that term.

Issues

Closes #111; closes #124.

[ecxyzzy]

Yeah I narrowed down the issue, it's just a data integrity problem that I need to resolve as I may have imported faulty data into the dev database. I'll do that at some point and re-request your review then.

Update for posterity: It was, in fact, not "just a data integrity problem"; the algorithm was inherently ill-suited to handle the myriad edge cases with the formatting of the UCI Registrar's Quarterly Academic Calendar, so I rewrote the calendar library using a more sane algorithm that locates the entries based on the keywords, rather than assuming that their locations relative to the table's first entry will remain constant.

This should also make it more extensible should we desire additional fields down the line.