Previously the path to ebin did not work properly when a different
folder structure was used. This makes sure that it targets the correct
folder.

(In future commits, this could even be a parameter, for better configurability)

OutputLog contains useful information about what happens with Pact
verification.

This is useful if the provider wants to use real authentication
flow for the contract tests.

Disclaimer:
`pactffi_verifier_add_custom_header` function unfortunately is not
able to override an existing header, so using this requires the pact
to not include the authorization header in the first place. This can
either be done by simply not using it on the consumer-side test or
removing it somehow before publishing the pact.

Although I worked through the following issues:
- pact-foundation/pact-net#460
- pact-foundation/pact-reference#275
from which the latter is actually marked as closed, and the fix is
allegedly included in the pact-ffi version that we use, it still did
not override an existing header. I tried bumping to a higher version
as well but without any luck. I will create an issue to pact-foundation
to try to get clarity on this.

This update should include the fix for overriding headers.

It was not as straightforward to track down, because it is not
marked in any release notes and the fix commit does not have a
concrete tag..., but:
- [This issue][1] was marked as completed on Feb 22
- [Pact FFI 0.4.17][2] was released on the same date
- 0.4.17 source code shows that the mentioned fix is present in
this version

[1]: pact-foundation/pact-reference#275
[2]: https://github.com/pact-foundation/pact-reference/releases/tag/libpact_ffi-v0.4.17