feat(go-feature-flag): add CustomHeaders option

[olvlvl]

This PR

Adds support for custom headers for every HTTP request, similar to the option found on the Ruby SDK. Custom headers can be used to define a User-Agent, to prevent requests from being blocked by servers that require browser-like identification or specific device signatures.

Notes

Our WAF requires the User-Agent header to be defined. Requests to the relay-proxy are being denied because the header is not specified.

[gemini-code-assist]

Summary of Changes

Hello @olvlvl, 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 enhances the GoFeatureFlag provider by adding the capability to include custom HTTP headers in all requests. This feature is crucial for environments where network infrastructure, such as WAFs, mandates the presence of specific headers like User-Agent to prevent request blocking. The change provides greater flexibility and compatibility for users deploying the GoFeatureFlag SDK in diverse network setups.

Highlights

• Custom HTTP Headers Support: Introduced a new CustomHeaders option allowing users to define arbitrary HTTP headers that will be included in all outgoing requests made by the GoFeatureFlag provider. This addresses scenarios where specific headers, like User-Agent, are required by intermediary systems such as Web Application Firewalls (WAFs).
• Integration into API Calls: The newly added custom headers are now applied to requests made by the CollectData and ConfigurationHasChanged API methods within the goff_api.go controller, ensuring consistent header application across key communication points.
• Comprehensive Testing: Updated unit tests for both the API controller and the main provider to include test cases for the CustomHeaders functionality, specifically verifying that a User-Agent header is correctly set and sent with requests.

Changelog

• providers/go-feature-flag/pkg/controller/goff_api.go
  • Added CustomHeaders map[string]string field to GoFeatureFlagApiOptions struct.
  • Modified CollectData method to iterate over CustomHeaders and set them on the HTTP request.
  • Modified ConfigurationHasChanged method to iterate over CustomHeaders and set them on the HTTP request.
• providers/go-feature-flag/pkg/controller/goff_api_test.go
  • Updated Test_CollectDataAPI test cases to include CustomHeaders in GoFeatureFlagApiOptions and assert the presence of the User-Agent header.
  • Updated Test_ConfigurationHasChanged test case to include CustomHeaders in GoFeatureFlagApiOptions and assert the presence of the User-Agent header.
• providers/go-feature-flag/pkg/provider.go
  • Propagated CustomHeaders from ProviderOptions to GoFeatureFlagApiOptions during provider initialization.
  • Added logic to create ofrep.WithHeaderProvider options for each custom header when initializing the ofrepProvider.
• providers/go-feature-flag/pkg/provider_options.go
  • Added CustomHeaders map[string]string field to ProviderOptions struct.
• providers/go-feature-flag/pkg/provider_test.go
  • Added lastRequestHeader http.Header field to mockClient to capture headers for assertion.
  • Modified roundTripFunc in mockClient to clone and store the request headers.
  • Updated TestProvider_BooleanEvaluation test cases to include CustomHeaders in ProviderOptions and assert the User-Agent header on outgoing requests.

Activity

• The pull request was opened by olvlvl with the title "feat: Add CustomHeaders option (GoFeatureFlag)".
• The author provided a detailed description explaining the motivation for adding custom headers, referencing a similar option in the Ruby SDK, and highlighting a specific use case involving WAF requirements for the User-Agent header.
• The changes involve modifications to the core API controller, provider options, and comprehensive test updates to support and verify the new functionality.

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[gemini-code-assist]

Code Review

This pull request adds a CustomHeaders option to the GoFeatureFlag provider, allowing users to set custom headers for all outgoing HTTP requests. This is a valuable addition, particularly for environments with WAFs that require specific headers like User-Agent.

The implementation is sound and well-tested. I've included a couple of suggestions to improve code clarity and reduce duplication. One suggestion is to refactor duplicated header-setting logic into a helper function in goff_api.go. Another is to simplify the code in provider.go by using the existing ofrep.WithHeader helper function.

Overall, this is a great contribution that enhances the provider's flexibility.

[erka]

/gemini review

[gemini-code-assist]

Code Review

This pull request introduces a valuable feature by allowing custom headers to be set for HTTP requests, which is particularly useful for scenarios requiring a User-Agent. The implementation is solid and includes corresponding test updates. My review includes a suggestion to address an inconsistency in how the Authorization header precedence is handled between different parts of the provider. Making this change will lead to more predictable and flexible behavior. Overall, great work on this enhancement.

[erka]

Thank you @olvlvl