usage segmentation

[brindy]

Task/Issue URL: https://app.asana.com/0/392891325557410/1206955287217877/f
Tech Design URL: https://app.asana.com/0/392891325557410/1208090005627335/f
CC:

Description:
This PR ads usage segmentation calculations to the app so that we can monitor usage across segments in a private way, without having to send granular usage information to the server.

Deviation from tech design:

• Added "Calculation" class / protocol in order to encapsulate the calculation logic exclusively and code it so that it's similar to the python implementation.

Steps to test this PR:

First run, new user:

1. Reset the simulator (so that the keychain is cleared)
2. Run the app
3. No m_retention_segments pixel should be fired

Subsequent run a few days later

1. Reset the simulator (so that the keychain is cleared)

2. Modify StatisticsLoader add the following line at the start of the load function:

        self.statisticsStore.atb = "445-1"
   

3. Run the app

4. An assertion failure should crash the app saying this is not a valid ATB.

5. Update the above line as follows and reset the simulator again:

        self.statisticsStore.atb = "v445-1"
   

6. Ensure that m_retention_segments pixel is fired. There will be various parameters but one should indicate "app_use" activity

7. Re-launch the app

8. No additional pixel should be fired

9. Perform a search

10. The pixel will be fired again and there should be a parameter indicating search activity.

11. Perform another search

12. No additional pixel should be fired

Return user test

1. Repeat the above test bit with the following atb. The pixels sent should include reinstaller in the segments parameter.

        self.statisticsStore.atb = "v445-1ru"
   

Definition of Done (Internal Only):

• Does this PR satisfy our Definition of Done?

[github-actions]

	Warnings
⚠️	PR has more than 500 lines of code changing. Consider splitting into smaller PRs if possible.

Generated by 🚫 dangerJS against ad4bda3

[aataraxiaa]

Mostly looks good @brindy , left some comments. Thanks for the useful documentation - it really helped in understanding, particularly for UsageSegmentationCalculator.

Also, tested and validated. One unit test is failing but I believe it’s unrelated.

[aataraxiaa]

Should we account for out-of-bounds here with something like:

guard range.lowerBound >= 0, 
              range.upperBound < self.count else {
     return nil
}   

and then return an Optional String.

[brindy]

Probably using min(self.count, range.upperBound) is better and more like you'd expect from a substring function. Annoying swift just doesn't provide these tbh

[aataraxiaa]

👍🏼

[aataraxiaa]

👍🏼

[aataraxiaa]

LGTM @brindy . Still a unit test failing - SyncManagementViewModelTests.testWhenSaveRecoveryPDFPressed_recoveryMethodShown(), which I assume is unrelated.