docs/cloudfront_realtime_log_config: document cf.logCustomData() log fields

[arditti]

Rollback Plan

If a change needs to be reverted, we will publish an updated version of the library.

Changes to Security Controls

No. This change is limited to website documentation and one acceptance test.

Description

CloudFront Functions gained a cf.logCustomData() helper method on 2026-07-14. A viewer request or viewer response function calls it to write a string into the access log record for that request, surfaced in two new log fields, viewer-request-log-data and viewer-response-log-data. Both are available to real-time log configurations and to standard logging (v2).

Neither field needs a schema change. aws_cloudfront_realtime_log_config.fields is an unvalidated TypeSet of TypeString, and aws_cloudwatch_log_delivery.record_fields constrains only list size (0–128) and per-element length (1–64), which the 23- and 24-character names clear. Both already accept the new names; what was missing was documentation saying so and an example of the end-to-end pattern.

• website/docs/r/cloudfront_realtime_log_config.html.markdown — put the existing example under a Basic Usage heading and added a Logging Custom Data From a CloudFront Function example pairing an aws_cloudfront_function that calls cf.logCustomData() with a log configuration that selects both fields, plus a note on wiring the cache behavior via function_association and realtime_log_config_arn. Extended the fields argument description.
• website/docs/r/cloudwatch_log_delivery.html.markdown — added a CloudFront Standard Logging (v2) example covering the delivery source → destination → delivery chain with both fields in record_fields. Since there is no first-class distribution-level standard logging (v2) resource yet (Add support for CloudFront Standard Logging (v2) to CloudWatch Logs #44832), this page is where CloudFront users land. The record_fields description now notes that valid field names vary by the source's log_type and links the CloudFront field reference.
• website/docs/r/cloudwatch_log_delivery_source.html.markdown — added CloudFront's ACCESS_LOGS to the log_type enumeration, which listed the other services but not CloudFront.
• internal/service/cloudfront/realtime_log_config_test.go — added TestAccCloudFrontRealtimeLogConfig_functionLogData, covering a configuration whose fields set contains both new names, with an import verification step.

No changelog entry: per docs/changelog-process.md, documentation updates and testing updates are both listed under changes that should not have one.

Relations

Closes #49176

References

• AWS announcement: https://aws.amazon.com/about-aws/whats-new/2026/07/cloudfront-functions-access-logs/
• Real-time log configuration fields (both new fields are the last two entries): https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/real-time-logs.html#understand-real-time-log-config-fields
• Standard logging (v2) field selection: https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/standard-logging.html#standard-logging-real-time-log-selection
• CloudFront Functions helper methods (logCustomData()): https://docs.aws.amazon.com/AmazonCloudFront/latest/DeveloperGuide/general-helper-methods.html#log-custom-data-method
• Relates Add support for CloudFront Standard Logging (v2) to CloudWatch Logs #44832 (first-class standard logging v2 support)

Output from Acceptance Testing

The new acceptance test has not been run — no AWS credentials for a suitable non-shared account were available in the environment this was prepared in. It provisions a Kinesis stream, an IAM role and policy, and a real-time log configuration. Local verification covers build, vet, format and test compilation:

% go build ./internal/service/cloudfront/ ./internal/service/logs/
% gofmt -l internal/service/cloudfront/ internal/service/logs/
% go vet ./internal/service/cloudfront/ ./internal/service/logs/
% go test -run 'xxNoSuchTestxx' ./internal/service/cloudfront/ ./internal/service/logs/
ok      github.com/hashicorp/terraform-provider-aws/internal/service/cloudfront 9.340s [no tests to run]
ok      github.com/hashicorp/terraform-provider-aws/internal/service/logs       8.952s [no tests to run]
% terrafmt diff ./website --check --pattern '*.markdown'

[github-actions]

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[ewbankkit]

LGTM 🚀.

[ewbankkit]

@arditti Thanks for the contribution 🎉 👏.

[github-actions]

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