[CAT-2382] Enable useSingleRequestParameter for Java Client Generator

[dvacca-onfido]

Summary

Enables the useSingleRequestParameter configuration option for the Java okhttp-gson client generator to prevent breaking changes when adding optional parameters to API methods.

Problem

Currently, when a new optional parameter is added to an API endpoint, the generated Java client adds a new parameter to the method signature. This creates a breaking change for existing implementations, forcing all consumers to update their code even if they don't need the new parameter.

Solution

The useSingleRequestParameter option changes the code generation pattern to use request builder objects:

Before (breaking changes on new optional params)

List<WorkflowRun> runs = onfido.listWorkflowRuns(applicantId, status, page, perPage, sort);
// Adding a new optional parameter 'createdAt' would break this code

After (backward compatible)

List<WorkflowRun> runs = onfido.listWorkflowRuns()
    .applicantId(applicantId)
    .status(status)
    .page(page)
    .execute();
// New optional parameters like .createdAt() can be added without breaking existing code

Benefits

• Backward Compatibility: Existing code continues to work when new optional parameters are added
• Forward Compatibility: New releases with additional optional parameters don't break consumer code
• Better API Design: Optional parameters are more discoverable and explicit
• Cleaner Code: Fluent API pattern is more readable, especially with many optional parameters

Changes

• Added useSingleRequestParameter: true to generators/java/okhttp-gson/config.yaml

Testing

• Configuration validated in generator test runs
• See companion PR in onfido-java repository for test adaptations

Migration Notes

This is a breaking change that requires updating all API method calls to use .execute(). However, once adopted, future changes will be non-breaking.

Related PRs

• [CAT-2382] Adapt Tests for useSingleRequestParameter Pattern onfido-java#170