Prevent potential crash during app teardown

[fractalwrench]

Goal

If the session API client is garbage collected while sessions are enqueued to be delivered, there
can be a crash when accessing self.config.apiKey from the operation queue. This changeset fixes that by copying the API key/session URL accessed from within the operation block.

Changeset

Copy the sessionURL and apiKey values so that self is not accessed from the operation block.

Tests

Existing unit tests/mazerunner.

Review

For the submitter, initial self-review:

• Commented on code changes inline explain the reasoning behind the approach
• Reviewed the test cases added for completeness and possible points for discussion
• A changelog entry was added for the goal of this pull request
• Check the scope of the changeset - is everything in the diff required for the pull request?
• This pull request is ready for:
  • Initial review of the intended approach, not yet feature complete
  • Structural review of the classes, functions, and properties modified
  • Final review

For the pull request reviewer(s), this changeset has been reviewed for:

• Consistency across platforms for structures or concepts added or modified
• Consistency between the changeset and the goal stated above
• Internal consistency with the rest of the library - is there any overlap between existing interfaces and any which have been added?
• Usage friction - is the proposed change in usage cumbersome or complicated?
• Performance and complexity - are there any cases of unexpected O(n^3) when iterating, recursing, flat mapping, etc?
• Concurrency concerns - if components are accessed asynchronously, what issues will arise
• Thoroughness of added tests and any missing edge cases
• Idiomatic use of the language

[snmaynard]

I feel like we might want to call cancelAllOperations in dealloc of the api client instead. Do you have thoughts @kattrali?

[fractalwrench]

@kattrali is Simon's suggestion something we might want to do, in addition to or in place of the fix that was originally proposed?

[kattrali]

Agree with Simon here, in dealloc, all operations should be cancelled to avoid starting a new operation while garbage collection is occurring.

[kattrali]

Both of these values should be copied