shippo: add HTTP test coverage

[20k-ultra]

Tests all shippo lib functions if they deserialize raw JSON correctly. Includes tests for pagination as well.

[20k-ultra]

ready for review

[20k-ultra]

Tests are failing because of cio_api. Other commits also have this failure so I do not suspect this PR to have introduced this.

failures:

---- applicants::tests::test_serialize_deserialize_applicants stdout ----
 INFO  tracing::span > new
thread 'applicants::tests::test_serialize_deserialize_applicants' panicked at 'called `Result::unwrap()` on an `Err` value: Timeout', cio/src/applicants.rs:2889:14
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace


failures:
    applicants::tests::test_serialize_deserialize_applicants

test result: FAILED. 7 passed; 1 failed; 7 ignored; 0 measured; 0 filtered out; finished in 30.00s

error: test failed, to rerun pass '-p cio-api --lib'
Error: Process completed with exit code 101.

[20k-ultra]

I'm still getting the same error after rebasing master and I see in master commits are passing so i'll look into it.

[20k-ultra]

hey @jessfraz, if I figure out the tests do you think this would get merged ? I spent a good bit of time on it so hoping it does.