Reduce duplication in session ending logic

[fractalwrench]

Goal

The existing implementation of SessionHandler duplicates business logic on how sessions should be ended. This changeset reduces that duplication & creates an explicit enum type that models the different way a session can end.

@bidetofevil would appreciate an in-depth review on this one, as it feels like there is a lot of complexity here.

Testing

Relied on existing unit test coverage in SessionHandlerTest.

[codecov]

Codecov Report

Merging #74 (4cdfd20) into master (503dde0) will increase coverage by 0.00%.
The diff coverage is 94.17%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master      #74   +/-   ##
=======================================
  Coverage   76.02%   76.02%           
=======================================
  Files         313      313           
  Lines       10095    10079   -16     
  Branches     1455     1457    +2     
=======================================
- Hits         7675     7663   -12     
+ Misses       1832     1827    -5     
- Partials      588      589    +1     

Files	Coverage Δ
...ndroid/embracesdk/session/EmbraceSessionService.kt	82.05% <82.35%> (-0.71%)	⬇️
...brace/android/embracesdk/session/SessionHandler.kt	89.02% <96.51%> (+1.30%)	⬆️

[bidetofevil]

Why are we bailing under this condition (and line 303 as well)? Shouldn't the caller just not call into this if that was the case? It feels weird for this code to have logic to check those conditions.

[fractalwrench]

This does feel a bit weird but the caller would have to check ~5 places, whereas the current code only checks 2 places. I'd propose changing this in a future PR

[bidetofevil]

Logic looks good. Most of my comments is about naming and flow and would make this code more readable. The name used and the number of variations depending on the combination of parameters can probably be simplified to reduce complexity, which there is a lot of here already....

[bidetofevil]

Awesome. Looks good!