Refactor & Integrate EOD Stock updates into Stock Ticker

[garettarrowood]

Summary

The initial work to select and integrate a Stock API has been accomplished. We will be using MarketStack, which provides 1,000 free stock price updates a month under a free plan. If our stakeholder wants more updates, we can talk to her about purchasing a paid plan.

The initial implementation isn't lengthy, but/and needs some re-architecting.

This issue can be completed in stages (multiple PRs) or all together. You may want to go create a free MarketStack account for yourself. It does not require you enter any financial info.

See criteria.

Things to Consider

#32
#37
#55

Criteria for Completion

• Move values into config instead leaving as constants in api files.
• Use Redis cache wrappers, as mentioned here
• Leverage ActiveModel, as mentioned here
• Consider using Faraday instead of Net::HTTP, as mentioned here
• More refactoring. Here's one relevant comment. Personally, I don't think any of this should be in models/, and may be better namespaced in an app/api/ directory where the classes are Api::Stock/etc.
• Rewire Stock prices integration #37 to use updated logic once the above bullets have been addressed.
• As a result of rewiring Stock prices integration #37 , the Stock Ticker will be functional and update daily.

[malsmr]

Is this ready to be worked on?

[garettarrowood]

@malsmr - Absolutely! - Please feel free to do some of the bullets and document any constraints concerns in regards to obtaining any others. Accomplishing this in multiple deliverables is fine by me.

[h-m-m]

We've gone with a different API and are generally breaking this work up into smaller issues