Unable to create plan jsonschema for device that extends Device until making it extend StandardReadable #1111

On i04 with a version of dodal ~1.49.0 and blueapi 1.0.0-rc.2 (with mx specific container), a plan with a DetectorMotion device as an argument was not able to create a plan JsonSchema. Making it extend StandardReadable instead worked?

stacktrace.txt

Steps To Reproduce

Steps to reproduce the behavior:

1. Create a plan that takes a DetectorMotion
2. Query the /plans endpoint
3. See attached stacktrace
4. Make the device extend StandardDetector instead
5. Reload the environment and query the /plans endpoint
6. Observe the plan is available

Acceptance Criteria

• We understand why or it doesn't happen anymore