test: fix missing env variable for backend test

[alcpereira]

Description

Currently the backend tests do not work locally:

 FAIL  server/test/acceptance/routes.test.js
  ● Test suite failed to run

    TypeError: OAuth2Strategy requires a clientID option

      17 |   //Discord authentication
      18 |   passport.use(
    > 19 |     new DiscordStrategy(
         |     ^
      20 |       {
      21 |         //Get client ID and Secret from discord developer portal
      22 |         clientID: process.env.DISCORD_CLIENT_ID,

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update
• This change requires an update to testing

Issue

• Is this related to a specific issue? If so, please specify:

Checklist:

• This PR is up to date with the main branch, and merge conflicts have been resolved
• I have executed npm run test and npm run test:e2e and all tests have passed successfully or I have included details within my PR on the failure.
• I have executed npm run lint and resolved any outstanding errors. Most issues can be solved by executing npm run format
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• My changes generate no new warnings