OpenAPIGenerator upgrade to v7.16.0 - [1] Added /Core classes and tests

[Kwok-he-Chu]

PR-1 of #1204

Description

This PR introduces the /Core classes needed for the upgrade of the OpenApiGenerator to v7.16.0 used in the Adyen sdk-automation to generate .NET models & services from the Adyen OpenAPI Specifications.

These core classes are required as part of the v7 upgrade in the openapi-generator .mustache templates: They are part of what the open-api-generation-tool outputs as code.

• /Auth wrap ApiKeys per API

• /Client to wrap ApiResponses (in the case of OK, BadRequest etc.)) and helper functions to add metadata to headers.

  • As part of these Client utilities, I had to move the existing functionality that constructs the LiveUrl to the new UrlBuilderExtensions.cs-class. The Adyen OpenApi (as of Nov 2025) do not contain the full live-url, and some of these APIs (e.g. Checkout, Pal ...) requires a liveUrlPrefix to go live.

• /Client/Extensions to provide helper functions to inject all services in your Dependency Injection service container and Retry/Timeouts extension functionality for the HttpClient (which previously handled here)

• /Converters to introduce (nullable) DateTimeOnly? and (nullable) DateOnly-fields.

  • As part of these converters, I had to also port our existing (Newtonsoft.Json) ByteArrayConverter.cs to the new native (System.Text.Json) ByteArrayConverter, which is used in ByteArray Byte[] deserialization/serialization.

• /Options - contains our classes (previously known as: Environment.cs, and Config.cs)to configure the AdyenOptions or AdyenEnvironment (Test/Live).

---

Change notes

Added new Core classes

Folder-structure

• Introduced a /Core-folder with the following functionality:
  • /Auth contains classes to add authorization to HttpHeaders.
  • /Client contains classes that wrap the ApiResponses and help-functionality to construct the LiveUrl (see UrlBuilderExtensions.cs)
  • /Client/Extensions/ contains the Polly-library that allows user to configure Timeouts, Retries and CircuitBreakers.
  • /Converters contains JsonConverters for DateOnly, DateOnlyNullable, DateTime and DateTimeNullable
  • /Options contains classes to configure the AdyenOptions or AdyenEnvironment (Test/Live).
• All APIs are now part of their own sub-folders
• Support DateTimeOffSet
  • Before: new DateTime(2025, 12, 25, 11, 59, 59)
  • -> After: new DateTimeOffset(2025, 12, 25, 11, 59, 59, TimeSpan.Zero)
• Support DateTimeOnly
  • Before: new DateTime(2025, 12, 25, 11, 59, 59)
  • -> After: new DateOnly(2025, 12, 25)
• Added Polly-library support for optional retries & circuitbreakers
• Added tests in /Core
• Use .NET8.0, and removed .NET6.0 as it has reached end-of-life support

[gemini-code-assist]

Summary of Changes

Hello @Kwok-he-Chu, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request is the initial phase of a larger effort to upgrade the OpenAPIGenerator to version 7.16.0. It introduces a foundational set of core classes and utilities, significantly restructuring the project to support modern .NET features and improve API interaction. Key changes include a new modular /Core directory, advanced HTTP client resilience policies via Polly, refined date/time serialization, and an update to the .NET 8.0 framework.

Highlights

• OpenAPIGenerator Upgrade: Introduced new /Core classes to facilitate the upgrade of the OpenAPIGenerator to v7.16.0, which is used for generating .NET models and services from Adyen OpenAPI Specifications.
• New Core Folder Structure: A new /Core folder has been added, containing sub-folders for /Auth (authorization), /Client (API responses, URL building, Polly integration), /Converters (JSON converters for various date/time types and byte arrays), and /Options (Adyen configuration).
• Enhanced Date/Time Handling: Added support for DateTimeOffset and DateOnly types, including dedicated JSON converters for both nullable and non-nullable versions, improving date and time serialization/deserialization.
• Resilience with Polly: Integrated the Polly library within /Client/Extensions/ to allow configuration of Timeouts, Retries, and CircuitBreakers for HTTP client requests, enhancing API call resilience.
• .NET Framework Update: The project now exclusively targets .NET 8.0, removing support for .NET 6.0, which has reached its end-of-life.
• API Structure and Utilities: APIs are now organized into their own sub-folders, and new utilities like HmacValidatorUtility for webhook signature validation and UrlBuilderExtensions for constructing live URLs have been added.

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[gemini-code-assist]

Code Review

This pull request introduces a significant upgrade to the OpenAPIGenerator and adds a new set of core classes, which is a great step forward. The code is generally well-structured. My review focuses on improving idempotency in some new extension methods, ensuring consistency in error handling within JSON converters, and enhancing the correctness and maintainability of the new tests. I've also noted that several test methods are unnecessarily marked as async. A major change is the removal of support for .NET 6.0, .NET Framework 4.6.2, and .NET Standard 2.0, making this a breaking change. The PR description mentions .NET 6.0 is EOL, which is not yet the case, so this should be clarified in the release notes.