Add jobs table, endpoint, and functionality

[leenyburger]

Feature

Why is this feature being added?

Allow jobs to be saved in the database and provided to the front end via an endpoint. This feature will also allow CRUD actions via the admin dashboard. See front end issue OperationCode/operationcode_frontend#982 for discussion.

What should your feature do?

Needs to include:

• new db table
• new GET index endpoint
• new resource in ActiveAdmin
• test coverage
• API docs

Jobs table to include:

• title
• source_url
• source
• city
• state
• country
• description
• status (i.e. active, inactive)
• remote
  Also include tagging.

[dmarchante]

@hpjaj Is there a reason the On Hold tag is applied here?

[dmarchante]

@leenyburger are you still working on this?

[jjhampton]

@dmarchante Looks like there is a PR that was submitted and is awaiting review/approval: #366

[kylemh]

Closing the related front-end ticket. When this is merged, please create issue in front-end

[apex-omontgomery]

This is available, @leenyburger did most of the work and if you want to finish up her efforts please see the following pr:
#366

[apex-omontgomery]

This is basically done, just waiting to figure out how to do prod db migrations.