[CHE-197] Add PG to BE Test Setup

[seantokuzo]

Description

• adds postgres service to the testing environments (test all / solo)
• sets environment variable values for testing environment
• creates a postgres test db initialization script (same as dev init script minus seeding)
• adds procedural script to test setup file to delete all rows from all tables before each test
• sets node-postgres pool's host dependent on NODE_ENV
• cleans up unused dotenv configuration in sql-db.ts
• removes unused environment variable declaration from test setup

Jira Task

JIRA TICKET

Testing Instructions

• run npm run docker-remove-all
• in the server/controllers/ directory, create a file named applications.test.ts and paste in the following code:

import request from 'supertest';
import app from '../app';

it('confirms pg test setup', async () => {
  const response = await request(app)
    .get('/api/applications/statuses')
    .set('Cookie', await login())
    .send({});

  expect(response.body[0].name).toEqual('Applied');
});

• run npm run docker-test:solo application
• confirm test is successful

Passing test confirms postgres test service is running, has been initialized with proper tables and base data, and that our pool can connect to it and run queries in our unit tests

Checklist

All Team Members

• I added a descriptive title to this PR.
• I filled out the Description, Jira Task, and Testing Instructions sections above.
• I added or updated [Jest unit tests]for any changes to components, server-side controllers, etc.
• I ran npm run docker-test in my local environment to check that this PR passes all unit tests.
• I did a quick check to make sure my code changes follow the recomended style guide.