Central request execution layer that normalizes JSON, raw, multipart, and form-encoded HTTP requests, injects auth headers, handles custom CA bundles, and implements auto-pagination with depth/limit controls. The execute* method family is a reusable pattern for building robust REST API clients with consistent error handling and pagination behavior, though it is tightly coupled to the Client struct.

Provides reusable httptest-based helpers such as setupMockServer, respondJSON, and paginatedResponse. This pattern is directly applicable to testing any REST client library and demonstrates a clean approach to mocking paginated JSON APIs without external dependencies.

Defines a structured UnexpectedResponseStatusError that captures HTTP status and body details. It is a simple, isolated error type that can be extracted and reused in any HTTP client to provide actionable error diagnostics instead of generic failures.