Enforce correct creation of Context #137
Description
What
Set a flag in the Context.managerState and assert that the same flag exists in the Context passed to each API method
Why
See OpenAssetIO/usdOpenAssetIOResolver#47 where the USD resolver plugin was not creating the Context properly, and it was only when prototyping a feature that required use of the managerState that it became apparent.
By making some use of the managerState, if only to store and check a boolean flag, we could have detected this problem early in the unit tests.