Add destroy request call in close event to support SSE closing (#34)

### Developer Checklist (Definition of Done)

**Issue**

- [x] All acceptance criteria from the issue are met
- [x] Tested in latest Chrome/Firefox

**UI/UX/Vis**

- [ ] Requires UI/UX/Vis review
  - [ ] Reviewer(s) are notified (_tag assignees_)
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  - [ ] Reviewer(s) approve of concept and design

**Code**

- [x] Branch is up-to-date with the branch to be merged with, i.e.,
develop
- [x] Code is cleaned up and formatted
- [x] Unit tests are written (frontend/backend if applicable)
- [x] Integration tests are written (if applicable)

**PR**

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for release notes later)
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- [x] [Summary of changes](#summary-of-changes) is written


### Summary of changes

- Destroy the current request on close to properly close any open SSE
(server side events) sessions. Otherwise, the sessions will remain open
and never be closed, causing issues with the reload process hanging
infinitely.

### Screenshots


### Additional notes for the reviewer(s)

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Thanks for creating this pull request 🤗

Author: puehringer

config/webpack.config.js

@@ -320,6 +320,10 @@ module.exports = (webpackEnv, argv) => {
               target: 'http://localhost:9000',
               secure: false,
               ws: true,
+              // Explicitly forward close events for properly closing SSE (server-side events). See https://github.com/webpack/webpack-dev-server/issues/2769#issuecomment-1517290190
+              onProxyReq: (proxyReq, req, res) => {
+                res.on('close', () => proxyReq.destroy());
+              },
             },
             '/login': {
               target: 'http://localhost:9000',