Add Mitigation model with GET routes

[ShaydeNofziger]

Fixes #37.

Description

This pull request adds a model, controller, GET API routes, and seed data for Mitigations.

Includes the following changes/additions:

• GET routes for retrieving mitigations from the API.
• apidocs documentation for the new GET routes.
• Seed data for event and teamtype now have explicitly defined id fields. This is necessary to ensure proper FK relation for mitigation seed data.
• Mitigation data field now has a formal standard, same with the type field.
• A new .github/ directory with a PULL REQUEST TEMPLATE for creating pull requests with useful details.
• knex.js has commented out lines of code for easily switching between Postgres and Sqlite3 in the development configuration.

Example Requests

Note: Append each route with the withRelated=event query param to include the associated event model in the response data.

• Retrieve all mitigations from the system.
  • GET /api/mitigation
• Retrieve all mitigations from the system corresponding to a given event_id.
  • GET /api/mitigation?event_id=[ID]
• Retrieve a specific mitigation by its id.
  • GET /api/mitigation/:id

Example Response (200)

{
  "id": 1,
  "type": "EVERY_ANY_ANY",
  "data": {
    "teamtypes": [1,2,3,4],
    "actions": [30],
    "reward_value": 3
  },
  "event_id": 1
}

Note: type is composed of 3 words that represent how the mitigation reward should be calculated by the system. It should be read as follows:

Give reward_value EVERY time ANY teamtypes performs ANY actions.

Valid type formats identified thus far:

• "EVERY_ANY_ANY"
  • Award the value for every time any team performed any of the actions.
  • Example: "-7 each if any team performed any action
• "EVERY_EVERY_EVERY"
  • Award the value for every time every team performed every action.
  • Functionally equivalent to "ANY_EVERY_EVERY".
  • Example: "-7 if all teams performed all actions."
• "EVERY_ANY_EVERY"
  • Award the value for every time any team performs every action.
  • Example: "-5 each if any team did every actions x,y, and z."
• "EVERY_EVERY_ANY"
  • Award the value for every time every team performs any action.
  • Example: "-3 each if every team did any actions x,y, or z."

Known Issues

This does not cover all of the seed data for mitigations. The basic "EVERY_ANY_ANY" cases were included, but additional work will need to be done to add in the remaining seeded/default mitigations.

Code coverage for /app/controllers/mitigation.js

Before	After
N/A	100%