187384622/new email model - PR3 - Add schema migration to drop old email columns and Adjust Relevant Dependencies

[perryzjc]

Pivotal Tracker Link

What this PR does:

This pull request is the third in a series intended to facilitate easier code review. The first PR can be found
here. The second PR can be found here.

For this PR, it aims to have a schema migration to drop the old email & personal_email column from Teacher model. It also adjust some old code that has dependencies on the old email fields. For example, personal_email || email_addresses.where(primary: false)&.pluck(:email)&.first now becomes email_addresses.find_by(primary: true)&.email

Include screenshots, videos, etc.

Original DB State

DB State : After rails db:migrate

Frontend works fine as before

Who authored this PR?

1. Perry (Jingchao) Zhong @perryzjc

How should this PR be tested?

1. Test the app work fine as before after dropping the old email columns
2. Also would be nice to ensure the code is clean that has no dependencies on the old email column anymore.

• Is there a deploy we can view?
• What do the specs/features test?
• Are there edge cases to watch out for?

Are there any complications to deploying this?

Yes. Run rails db:migrate to apply the migration.

Checklist:

• Has this been deployed to a staging environment or reviewed by a customer?
• Tag someone for code review (either a coach / team member)
• I have renamed the branch to match PivotTracker's suggested one (necessary for BlueJay) (e.g. michael/12345-add-new-feature Any branch name will do as long as the story ID is there. You can use git checkout -b [new-branch-name])

[ArushC]

This is good.