feat: scaffolding work of rest catalog client

[HeartLinked]

This PR introduces the foundational scaffolding for the Iceberg REST Catalog client implementation in C++. It establishes the core infrastructure for communicating with Iceberg REST Catalog servers following the Iceberg REST Catalog Specification.

Key Components Added

1. HTTP Client Infrastructure (http_client.h/cc)

• Implemented HttpClient class wrapping the CPR library for HTTP operations.
• Supports GET, POST, POST (form-urlencoded), HEAD, and DELETE methods.
• Thread-safe session management with mutex protection.
• HttpResponse wrapper to abstract underlying HTTP library implementation.

2. Configuration Management (catalog_properties.h/cc)

• RestCatalogProperties class for REST catalog configuration.

3. Resource Path Construction (resource_paths.h/cc)

• ResourcePaths class for building REST API endpoint URLs.

4. Error Handling Framework (error_handlers.h/cc)

• Hierarchical error handler design following the REST specification.
• HTTP status code to ErrorKind mapping.
• Also, extended result.h with new rest related error kinds.

5. REST Utilities (rest_util.h/cc)

• URL encoding/decoding (RFC 3986 compliant via libcurl).
• Namespace encoding/decoding with ASCII Unit Separator (0x1F).
• Configuration merging with proper precedence (server overrides > client config > server defaults).
• String utilities (e.g., TrimTrailingSlash).

7. RestCatalog Implementation (rest_catalog.h/cc)

• RestCatalog class implementing the Catalog interface.
• Initialization workflow:
  1. Validates client configuration.
  2. Fetches server configuration from /v1/config.
  3. Merges server and client properties.
  4. Updates resource paths based on final configuration.

Testing

• rest_util_test.cc: Comprehensive tests for URL encoding/decoding, namespace encoding, config merging.
• rest_catalog_test.cc: These currently introduced tests are merely temporary integration tests that require a local REST server, such as the apache/iceberg-rest-fixture Docker image While this enables local testing, it is incompatible with the GitHub CI process, so they have been marked as DISABLED_. In the future, we aim to follow the example of iceberg-rust by designing comprehensive integration tests to verify the REST catalog client's behavior and integrating them into our GitHub CI pipeline. This work is scheduled for later completion; please refer to issue Implement REST Catalog Integration Tests with Docker in CI Pipeline #333.

[wgtmac]

I just did an initial pass, the main concerns are:

1. URL encoding & decoding may not match the Java impl.
2. Namespace encoding is using the deprecated 0x1F.
3. ErrorResponse and ErrorModel are duplicate. We can improve it by using a single ErrorResponse.

Missing test cases of:

1. Catalog properties to extract header map.
2. All functions in the rest_util.h, check TestRestUtil.java.
3. Resource paths, check TestResourcePaths.java.

Since this is a large PR and we don't have good test fixture for it yet, I'm fine to add them later by adding TODOs.

[Jinchul81]

Why did you apply this change? I would prefer constexpr std::string_view instead of const std::string.

[wgtmac]

The main reason is that we still need to wrap it with std::string every time to create http headers.

[HuaHuaY]

So @HeartLinked may need to remove std::string(...) wrapper in some files, such as src/iceberg/catalog/rest/config.cc.

[Jinchul81]

Why did you disable the test? Leave a comment with a reason.

[HeartLinked]

This is a temporary integration test that requires a local REST server, such as the Docker image apache/iceberg-rest-fixture provided by Apache Iceberg. Currently, this method allows testing locally, but it obviously cannot pass the Github CI process, so it is a temporary expedient. In this first version PR, we clearly cannot comprehensively complete such a large amount of work. You can take a look on this issue: #333 :)

[wgtmac]

The main reason is that we still need to wrap it with std::string every time to create http headers.

[wgtmac]

Thanks all for the review! Great job @HeartLinked. Let me merge this to move forward.