Added config to run the idp login locally

With this MR, we are able to use idp login with running docker-compose and the frontend on http://localhost:3000.

There is also the need for the up to date oidc client id - as this is sensible information, we distribute this file on other ways.

You can ask @mhanisch, @schaffem or @nils for getting this info.

The file itself just looks like this

NUXT_ENV_CLIENT_ID=AABBCCDDEEFFGGHHIIJJKK

For the moment the idp doesn't work with the port 3000, but @schaffem is asked to add it.