fix: create blueapi cache folder on login

[NeilSmithDLS]

Check for the existence of the blueapi cache folder on login and if it doesn't exist create it.

fixes 1448

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.35%. Comparing base (85cd819) to head (d4b4d28).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1520   +/-   ##
=======================================
  Coverage   95.34%   95.35%           
=======================================
  Files          43       43           
  Lines        3200     3205    +5     
=======================================
+ Hits         3051     3056    +5     
  Misses        149      149           

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[tpoliaw]

Do we need to create the directory on load? If it doesn't exist, I imagine this will behave the same as if the cache file doesn't exist which is (hopefully) already handled.

[NeilSmithDLS]

If you look in the stack trace on the ticket there were 2 errors thrown, the first when trying to open the file in this method, and the second when calling can_access_cache as part of the error handling for the first error.

If it is correct that this method should error and fall back on the error handling if the folder doesn't exist, then this can be removed, otherwise it does need to stay

[tpoliaw]

I think load_cache will still throw the exception when the file doesn't exist so creating the directory doesn't really achieve much. The second exception where it can't start the device flow does need the directory to be present.

It doesn't really matter though so feel free to leave it if it would otherwise hold up the bug being fixed.

[NeilSmithDLS]

?