Fix flaky IdentityLinker test

[mitchellhenke]

🛠 Summary of changes

I got a test failure this morning due to a time-based flakiness:

Failures:
  1) IdentityLinker#link_identity identity.verified_at the request is includes identity proofing and verified_at is not null does not set the timestamp
     Failure/Error:
       expect(
         user.last_identity.verified_at,
       ).to be_within(1.second).of(1.week.ago)
       expected 2024-06-05 00:46:12.000000000 +0200 to be within 1 of 2024-06-05 00:46:13.011929850 +0200
     # ./spec/services/identity_linker_spec.rb:236:in `block (5 levels) in <top (required)>'
     # ./spec/support/fake_analytics.rb:181:in `block (2 levels) in <top (required)>'

This PR freezes time for the test to make it more reliable

[aduth]

Does this risk bleeding into tests run after this one? In other tests we use around like this, to ensure the teardown:

around do |example|
  feeze_time { example.run }
end

[mitchellhenke]

The teardown here should take care of it: https://api.rubyonrails.org/v7.1.1/classes/ActiveSupport/Testing/TimeHelpers.html#method-i-after_teardown

I did some testing and it seems to be called after every test.

[aduth]

Interesting. It definitely seems easier to just have the one line of code, though generally speaking I feel a little uneasy about any sort of side-effecty code like this inside a test case.

[mitchellhenke]

I was hoping to have the freeze_time block around it, but the helper doesn't like nested time traveling blocks:

     RuntimeError:

       Calling `travel_to` with a block, when we have previously already made a call to `travel_to`, can lead to confusing time stubbing.

       Instead of:

          travel_to 2.days.from_now do
            # 2 days from today
            travel_to 3.days.from_now do
              # 5 days from today
            end
          end

       preferred way to achieve above is:

          travel 2.days do
            # 2 days from today
          end

          travel 5.days do
            # 5 days from today
          end