feat(server): Add pull session status websocket handler (#2016)

[andre-code]

PR to add session status websocket handler.

• (ui) Always check if there are changes in the session status using the websocket channel.
• (ui) Ignore changes if the pathname is a sessionUrl (*/sessions,*/sessions/new, */sessions/show/* ).
• (ui) if there is a change and the pathname is not a session page pull the session using the NotebooksCoordinator.
• (server-ui) Add websocket handler that check the sessions status object and send a message ("true") when there is a change.
• Add Tests

Closes #2016

/deploy #persist

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-ui-2145.dev.renku.ch

[lorenzo-cavazzi]

The PR looks good! I have just a couple of changes, mainly to:

• prevent handling the auth headers in the low-level fetch functions
• store the minimum amount of data necessary when using channel.data.set

[lorenzo-cavazzi]

Great, almost there! I have just another detail on how we handle server-side headers so that we can keep that coherent with the changes already done in the kg-search branch.

[lorenzo-cavazzi]

Great! This works well!
I tested a bit more with anonymous users and I submitted a change to clean the headers (it should work but give it a quick test) along with a couple of other cosmetic changes. Nothing big, the PR is basically ready.

Also, give a run to npm run lint on the "server" folder. There are a couple of lining errors but somehow the tests are not failing on that

[lorenzo-cavazzi]

This works well! Let's merge it 🚀

[RenkuBot]

Tearing down the temporary RenkuLab deplyoment for this PR.