RCORE-2061: Fix handling backlink column as last element in KeyPath

[jedelbo]

What, How & Why?

Fixes #7530
We should also check that right column key is changed when checking a backlink column

☑️ ToDos

• 📝 Changelog update
• 🚦 Tests (or not relevant)
• C-API, if public C++ API changed
• bindgen/spec.yml, if public C++ API changed

[jedelbo]

@papafe if you feel for it, you may want to check is this fixes the problem.

[coveralls-official]

Pull Request Test Coverage Report for Build jorgen.edelbo_396

Details

• 42 of 42 (100.0%) changed or added relevant lines in 3 files are covered.
• 74 unchanged lines in 19 files lost coverage.
• Overall coverage increased (+0.004%) to 91.112%

---

Files with Coverage Reduction	New Missed Lines	%
src/realm/dictionary.cpp	1	85.16%
src/realm/index_string.cpp	1	85.1%
src/realm/mixed.cpp	1	86.75%
src/realm/sync/noinst/server/server_history.cpp	1	62.92%
src/realm/util/serializer.cpp	1	90.43%
test/test_index_string.cpp	1	93.48%
src/realm/array_blobs_big.cpp	2	98.58%
src/realm/query_expression.hpp	2	93.81%
src/realm/collection_parent.cpp	3	93.08%
src/realm/sync/instruction_replication.cpp	3	91.8%

Totals
Change from base Build 2567:	0.004%
Covered Lines:	217408
Relevant Lines:	238617

---

💛 - Coveralls

[nicola-cab]

great fix!

[tgoyne]

This broke a pretty straightfoward Swift test:

    func testBacklinkPropertyKeyPathNotifications2() {
        let realm = try! Realm()
        realm.beginWrite()
        let person = realm.create(SwiftOwnerObject.self)
        let dog = realm.create(SwiftDogObject.self)
        person.dog = dog
        try! realm.commitWrite()

        // Expect no notification for "owners" when "owner.name" is changed
        let ex = expectation(description: "no change notification")
        let token = dog.observe(keyPaths: ["owners"], { _ in
            ex.fulfill()
        })
        try! realm.write {
            let owner = dog.owners.first!
            owner.name = "Tom"
        }
        waitForExpectations(timeout: 0.1, handler: nil)
        token.invalidate()
    }

This modification is now incorrectly producing a notification.