New debug client

[testower]

Summary

We want to replace the old OTP UI, nowadays called the "Debug UI". The old UI uses the deprecated REST API, is not maintained and is based on an old tech stack. So, we (OTP Developer meeting) have decided to make a new UI. The new UI will use the Transmodel GraphQL API.

The goal for the UI is to support OTP developers in day to day work with OTP. If you are looking for a UI to deploy as a service to the public we recommend looking at other options. Ask in the gitter chat for the latest and best option for you.

Note: This PR does not replace the old debug client. We will do this in a later PR. There is more work to be done before we want to remove the old one completely.

Issue

Relates to #5330

Unit tests

No tests for the debug client.

Documentation

There is a README in the new source code folder for now.

Changelog

✅

Bumping the serialization version id

No

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (79d1cbc) 66.27% compared to head (2dbaa8b) 67.24%.
Report is 1110 commits behind head on dev-2.x.

Additional details and impacted files

@@              Coverage Diff              @@
##             dev-2.x    #5334      +/-   ##
=============================================
+ Coverage      66.27%   67.24%   +0.97%     
- Complexity     15171    16084     +913     
=============================================
  Files           1789     1852      +63     
  Lines          69275    70970    +1695     
  Branches        7351     7399      +48     
=============================================
+ Hits           45910    47724    +1814     
+ Misses         20881    20781     -100     
+ Partials        2484     2465      -19     

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[testower]

It doesn't show in the check list below 👇 but I added a temporary workflow for verifying the frontend build (linter, formatter, typescript compiler and vite build), until we decide where it should live permanently.

https://github.com/entur/OpenTripPlanner/actions/workflows/client-build.yml

[testower]

There are still some outstanding tasks from the issue, I was hoping to get those done in separate pull requests.

[leonardehrenfried]

As I said in today's meeting: I haven't read the code and don't feel that I need to. The integration with the rest of the system is minimal and good enough for a first version.

[daniel-heppner-ibigroup]

I looked through the code and thought it was nicely written and fairly simple. I was able to see what was going on at a glance, which was nice.

[vesameskanen]

Clean, modern and simple react app. Works without problems with our GTFS data.

[t2gran]

I merged this with just one approval, @leonardehrenfried had already approved it, and @daniel-heppner-ibigroup also gave it a +1 review. I hope that is ok.