Fix database migration issue with different database models (#20214 cherry pick on 21.7.2)

[mokagio]

Cherry picks the changes from #20214 onto 21.7.2.

Below the original PR description by @wargcm:

---

Partially fixes #20207

Description

• Fixes a logic issue with the existing migrate model functions. Refer to the old Obj-C function here:

  WordPress-iOS/WordPress/Classes/Utility/ContextManager.m

  Line 219 in 24db036

  BOOL migrationNeeded = ![self.managedObjectModel isConfiguration:nil compatibleWithStoreMetadata:metadata];

• First attempts to manually migrate the database with existing functions
• If the manual migration fails, fall back to an automatic migration: https://developer.apple.com/documentation/coredata/using_lightweight_migration#2903991

Note
This does not fix the migration issue with 21.8 WordPress -> 21.7 Jetpack. It only fixes 21.7 WordPress -> 21.8 Jetpack. To fix both scenarios, these changes would need to be applied to the 21.7 branch.

Testing

To test:

WP -> JP Migration fix

• Checkout the release/21.7.1 branch
• Install WordPress and login
• Begin the migration with any of the Jetpack powered banner entry points
• Checkout this branch issue/20207-fix-model-jp-migration
• Install Jetpack and launch
• Verify your data was migrated successfully

App upgrade

• Checkout the release/21.7.1 branch
• Install WordPress and login
• Install Jetpack and login
• Checkout this branch issue/20207-fix-model-jp-migration
• Install WordPress and launch
• Verify you are still logged in with your data
• Install Jetpack and launch
• Verify you are still logged in with your data

Regression Notes

1. Potential unintended areas of impact
   Potentially with the existing manual model migration functions

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   Manually testing the app upgrade scenario and comparing code to older working code

3. What automated tests I added (or what prevented me from doing so)
   N/A

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[mokagio]

@wargcm, the original PR description said "Partially fixes #20207". I assume the partially was because of what was explained below "This does not fix the migration issue with 21.8 WordPress -> 21.7 Jetpack. It only fixes 21.7 WordPress -> 21.8 Jetpack. To fix both scenarios, these changes would need to be applied to the 21.7 branch."

So, I'd say this PR fully fixes #20207?

[dvdchr]

So, I'd say this PR fully fixes #20207?

Yes, that's correct @mokagio 👍🏼

[wpmobilebot]

You can test the changes in Jetpack from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr20217-f353613 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[wpmobilebot]

You can test the changes in WordPress from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr20217-f353613 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[dvdchr]

LGTM .

Since this is also going to be shipped on the 21.8 beta, I've tested and verified that these scenarios work:

• WP 21.7 App Store -> JP 21.8 beta with PR #20214 ✅
• WP 21.8 TestFlight -> JP 21.7.2 (this PR) ✅
• WP 21.8 beta -> JP 21.8 beta with PR #20214 ✅
• WP 21.7.2 (this PR) -> JP 21.7.2 (this PR) ✅