Enhance/conformu

[ppp-one]

This pull request makes several important improvements and corrections to the camera API simulator, focusing on stricter validation, improved error handling, and better adherence to the ASCOM standard for gain/offset and sub-exposure controls. The changes also refactor some behaviors to more accurately simulate real hardware, particularly for subframe validation and pulse guiding.

Key changes include:

Validation and Error Handling Improvements

• Subframe geometry (NumX/NumY/StartX/StartY) is now strictly validated in start_exposure, ensuring that binned subframes are within camera bounds. Setters for these values now only reject obviously invalid input, while full validation is deferred to exposure start. [1] [2] [3] [4] [5]
• Error codes have been updated throughout to better match ASCOM conventions, and several endpoints now raise PropertyNotImplemented errors when a feature is not supported (e.g., sub-exposure duration, gain/offset min/max). [1] [2] [3] [4] [5]

Gain and Offset List Mode Compliance

• The camera now operates in "list mode" for both gain and offset: values are integer indices into the respective lists, and min/max endpoints return PropertyNotImplemented as required by ASCOM. The API models and validation logic have been updated accordingly. [1] [2] [3] [4] [5] [6]

Pulse Guiding Simulation

• Pulse guiding is now simulated asynchronously: the ispulseguiding flag is held true for the requested duration, then cleared, more closely matching real hardware behavior.

Miscellaneous Corrections

• Fast readout and CCD temperature endpoints now check capabilities and use correct error codes. [1] [2] [3]
• Exposure duration endpoints now properly handle the case where no exposure has been taken. [1] [2]
• The image cache key now includes subframe and binning parameters for better cache accuracy. [1] [2]