* Added /device/token handler with associated business logic and storage tests.
Perform user code exchange, flag the device code as complete.
Moved device handler code into its own file for cleanliness. Cleanup
* Removed PKCE code
* Rate limiting for /device/token endpoint based on ietf standards
* Configurable Device expiry
Signed-off-by: justin-slowik <justin.slowik@thermofisher.com>
