You'd have to write the contract tests. VCR is similar, you could probably meta-program it but I wouldn't. I would just do one or two and see how it goes.
I tried Polly a long time ago (because I missed VCR) and didn't have a great time.
Also, VCR is more like a magic mock. Pact is sort of a different type of testing tool. A typical CI flow (to me would be something like this)
• unit tests (which ideally would not need VCR)
• integration tests (which could use VCR for conveniences)
• contract tests (which are trying to enforce many-service interactions)
Theses are different levels and styles usually using different libraries.
• unit tests (rspec)
• integration tests (maybe rspec's request specs, but now you need bigger libraries)
• contract tests (pact)
I know some Ruby apps are all mixed up (take Rails) where there are not clean lines between the things. But you'll probably find yourself over time on a project not running the end-to-end tests that much and now you've filtered the tests for productivity. And you'd do the same in a CI pipeline where each test step is fancier and fancier.
Essentially, the testing pyramid.
• It tells you what to write
• It also kind of tells you what order your tests should run in (pact is beyond the peak)