[P1] Repair and enable disabled integration tests

As of #47, we are running integration tests in Github Actions. However, we are only running a subset of the available tests. We should repair the following tests and enable them in .github/workflows/integration_tests.yaml:

yarn test:integration:data_access: All of these tests are failing due to misuse of Knex in the Users module:

  14) users module
       "before all" hook in "users module":
     TypeError: knex(...).where(...).first(...).bind is not a function
    at Function.UsersModule.createNewUser (server/lib/data_access/users.coffee:138:4)

yarn test:integration:firebase: In order to run Firebase tests, we need to create a Firebase Realtime Database which can be used by Github Actions.

There are also tests which are commented out and need to be reworked, either because they were broken or because they were too slow:

% git grep -l 'Test disabled'
test/integration/achievements/collector_supreme.js
test/integration/achievements/home_turf.js
test/integration/achievements/seven_sisters.js
test/integration/data_access/cosmetic_chests.js
test/integration/data_access/inventory.js
test/integration/data_access/migrations.js
test/integration/data_access/rift.js
test/integration/data_access/users.js