fix: support httpmock generation for array types

[danieleades]

closes #1260

Http mock generation fails for me at compile time because it assumes that all types implement Display. This doesn't hold for vectors.

Summary

• Fix httpmock query-parameter generation for non-Display types by reusing QueryParam serialization and matching on decoded (key, value) pairs.
• Add query_param_pairs in progenitor-client to mirror QueryParam rules (scalars, arrays with repeated keys, objects/maps), and use it throughout generated httpmock matchers.
• Add compile-only coverage plus a minimal OpenAPI spec for array query parameters.

Notes

• The matcher helper applies decoded pairs, which is why this shows up in many places (not just arrays).
• Serialization failures now expect because these are non-recoverable errors in generated mocks/tests.

[danieleades]

this now works against my openAPI spec.

note the need to convert &str to String to satisfy the trait bounds of httpmock json_body_obj. That bound appears however to be a bug- have opened a PR upstream - httpmock/httpmock#206

[danieleades]

marking as a draft until the upstream issue in httpmock is resolved

[danieleades]

upstream fix has been merged, just need a new release of httpmock

[danieleades]

@ahl - would it be possible to trigger CI for this one?

this issue is a blocker for me adopting progenitor