refactor: allow any token retriever in the rest client

[jacob720]

See https://confluence.diamond.ac.uk/pages/viewpage.action?pageId=398853592&spaceKey=DCT&title=04-06-2026
Currently the rest client requires a session manager to handle retrieving auth tokens. I've made it more flexible so that it now accepts anything with a get_valid_access_token method, so a UDC client can use the same rest client.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.61%. Comparing base (ab2ebc6) to head (8e1d330).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1553   +/-   ##
=======================================
  Coverage   95.61%   95.61%           
=======================================
  Files          43       43           
  Lines        3214     3215    +1     
=======================================
+ Hits         3073     3074    +1     
  Misses        141      141           

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[DominicOram]

Thanks, I think we want SessionManager to explicitly implement TokenRetriever though, right?

I also think we should add the UDCTokenRetriever (from https://github.com/DiamondLightSource/daq-queuing-service/pull/40/changes) into BlueAPI proper, it seems like a reasonable thing to have in here. Though maybe @tpoliaw disagrees?

[tpoliaw]

Thanks - this makes things simpler and should help when we come to refactor the login stuff in #1381.

Possibly a bit picky but can the protocol be called TokenSource or TokenProvider or similar. It's not really retrieving it if it's generating a new one and blueapi shouldn't care where it comes from.

I think we want SessionManager to explicitly implement TokenRetriever though, right?

It can do but I don't think it needs to.

I also think we should add the UDCTokenRetriever into BlueAPI proper

I'm not against the UDC ServiceAccount provider being in blueapi core but it doesn't need to be in this PR.

[tpoliaw]

Suggested change

	def __init__(self, session_manager: TokenRetriever | None):
	def __init__(self, token_source: TokenRetriever | None):

[tpoliaw]

Suggested change

	_token_retreiver: TokenRetriever | None
	_token_retriever: TokenRetriever | None