Convert event.app from NSDictionary to a structured class

[fractalwrench]

Goal

Converts event.app from an NSDictionary to a structured class where each field is represented as a property.

BugsnagApp is used for sessions, and contains stateless properties that do not change over the lifecycle of an application. BugsnagAppWithState extends this class and is used for events, and contains stateful properties that change for each error - e.g. durationInForeground.

Changeset

• Added BugsnagApp and BugsnagAppWithState classes with properties for each field in the spec
• Updated BugsnagConfiguration to have a default value for appType, rather than parsing in the BugsnagEvent
• Altered BugsnagEvent to use readonly BugsnagAppWithState for event.app
• Refactored BSGParseApp and BSGParseAppWithState methods into new BugsnagApp classes, so that they can parse a KSCrash report and populate their fields
• Extracted JSON serialization into BugsnagApp/WithState from BugsnagEvent
• Removed app.name as it is the same as app.id

Tests

• Added unit test to verify that BugsnagApp and BugsnagAppWithState populate correctly, and that they serialize JSON correctly
• Updated existing test coverage
• Ran example app and verified that app data is sent to the dashboard for an event

[robinmacharg]

From what I understand, looks good. And 68% coverage on unit tests, which is definitely going in the right direction! Couple of in-line comments, mostly opinionated nits over formatting.

Is it worth putting new structured containers in a group in XCode to make working with them easier? Assuming that the podspec needs updated to match any folder nesting. The list of files is now considerable (i.e. more than a screen-full). Failing that the new additions should be arranged alphabetically in XCode.

[fractalwrench]

Is it worth putting new structured containers in a group in XCode to make working with them easier?

This is definitely worth doing - I'll raise a separate PR to address this.

[robinmacharg]

Looking good.