fix: improve error handling when request receives non-JSON response

[NeilSmithDLS]

improve error handling when request receives non-JSON response.

Closes 1472

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.22%. Comparing base (774781b) to head (a6ad517).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1477      +/-   ##
==========================================
+ Coverage   95.21%   95.22%   +0.01%     
==========================================
  Files          43       43              
  Lines        3132     3144      +12     
==========================================
+ Hits         2982     2994      +12     
  Misses        150      150              

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[tpoliaw]

I'm not sure the _exception method is the best place for this check to be, for instance running a plan uses the alternative _create_task_exceptions method and bypasses this check

$ # with config pointing to oauth-proxy
$ uv run blueapi -c path/to/config.yaml controller run --bg -i cm12345-3 sleep '{"time": 3}'
Error: task could not run: Expecting value: line 1 column 1 (char 0)

We're also parsing the json multiple times on the happy path when everything is working which isn't ideal.

Would it work to add a helper method to wrap wherever we're calling .json()?

[tpoliaw]

This is much better, thanks. A couple of more minor comments if you want to look at them but this is a big improvement over the stacktrace it gave before.