fix: ApplyV1Options nil tags map

[genesor]

What does this PR do?

Fixes #3955

During the creation of v1.74.0 the new function ApplyV1Options allowing us to transform v1 StartSpanOptions into v2 was introduced.

Assigning tags manually via cfg.Tags["x"] = "foo" was working in previous v1 because the cfg was already tagged internally by the roundtripper but the cfg in the function in ApplyV1Options uses an empty and untagged StartSpanConfig with a nil map.

Reviewer's Checklist

• Changed code has unit tests for its functionality at or near 100% coverage.
• System-Tests covering this feature have been added and enabled with the va.b.c-dev version tag.
• There is a benchmark for any new code, or changes to existing code.
• If this interacts with the agent in a new way, a system test has been added.
• New code is free of linting errors. You can check this by running ./scripts/lint.sh locally.
• Add an appropriate team label so this PR gets put in the right place for the release notes.
• Non-trivial go.mod changes, e.g. adding new modules, are reviewed by @DataDog/dd-trace-go-guild.

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[datadog-datadog-prod-us1]

⚠️ Tests

⚠️ Warnings

🧪 5 Tests failed

TestGeneratedSpan from gopkg.in/DataDog/dd-trace-go.v1/contrib/envoyproxy/go-control-plane (Datadog)

Failed

=== RUN   TestGeneratedSpan
--- FAIL: TestGeneratedSpan (0.03s)

TestGeneratedSpan/request-span from gopkg.in/DataDog/dd-trace-go.v1/contrib/envoyproxy/go-control-plane (Datadog)

Failed

=== RUN   TestGeneratedSpan/request-span
    envoy_test.go:48: 
        	Error Trace:	/home/runner/work/dd-trace-go/dd-trace-go/contrib/envoyproxy/go-control-plane/envoy_test.go:236
        	            				/home/runner/work/dd-trace-go/dd-trace-go/contrib/envoyproxy/go-control-plane/envoy_test.go:48
        	Error:      	Received unexpected error:
        	            	EOF
        	Test:       	TestGeneratedSpan/request-span
2025/09/09 15:06:22 Datadog Tracer v2.2.3 ERROR: external_processing: the body parsing has been wrongly configured. Please disable in your Envoy External Processor filter configuration the body processing mode and enable the allow_mode_override option to let the processor handle the processing mode. (occurred: 09 Sep 25 15:06 UTC)
...

TestGeneratedSpan/span-with-injected-context from gopkg.in/DataDog/dd-trace-go.v1/contrib/envoyproxy/go-control-plane (Datadog)

Failed

=== RUN   TestGeneratedSpan/span-with-injected-context
    envoy_test.go:83: 
        	Error Trace:	/home/runner/work/dd-trace-go/dd-trace-go/contrib/envoyproxy/go-control-plane/envoy_test.go:236
        	            				/home/runner/work/dd-trace-go/dd-trace-go/contrib/envoyproxy/go-control-plane/envoy_test.go:83
        	Error:      	Received unexpected error:
        	            	EOF
        	Test:       	TestGeneratedSpan/span-with-injected-context
2025/09/09 15:06:22 Datadog Tracer v2.2.3 ERROR: external_processing: the body parsing has been wrongly configured. Please disable in your Envoy External Processor filter configuration the body processing mode and enable the allow_mode_override option to let the processor handle the processing mode. (occurred: 09 Sep 25 15:06 UTC)
...

View all

ℹ️ Info

❄️ No new flaky tests detected

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