123 body index refactor modularization

[ChromaticPanic]

This PR moves majority of the algorithms out of the Body component into a common module so that unit testing of these functions and debugging is less complicated.

• Ref #123

Common Module

• api
  • App calls that need to go over the internet
• cacheutils
  • CRUD operations on the imageCache data structure
• error
  • Custom Error classes
• types.d.ts
  • common shared data model for the front end
  • definitions of the expected structures from backend

Hooks Module

• useBackendUrl
  • memoized hook to provide the back end URL
• useDicoderTiff
  • hook entry point to the Tiff decoder

Quality of life changes Pure Functions

• Functions were converted into pure functions for easier debugging and predictability

Body Component

• useEffect dependencies were simplified to reduce the number of chain dependencies
  • This fixed some rendering issues referenced below

directory_list

• Separated Container and View
  • Example showing separation of Component state and view
  • Useful for large complicated components
  • Placing component code in a tsx file with the same name will make it slightly easier to debug since the browser console will indicate the file name of the component with an error or exception

Unit Tests

• Multiple strategies for testing the different components are present
  • single vs parametric test case scenarios
  • different dependency mocking strategies

Fixes

• Fixes #122
• An issue where bounding boxes are shown for a different image
• An issue where the first image is obscured by the default image placeholder