[OpenTelemetry] Support Schema URL for resources

[martincostello]

Fixes #6696

Changes

• Add support for including a schema URL for resources.
• Print the schema URL in the console exporter.
• Serialize the schema URL in the OTLP exporter.

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 91.66667% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.11%. Comparing base (2d50a2b) to head (9a9c0ad).
⚠️ Report is 9 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...emetry.Exporter.Console/ConsoleActivityExporter.cs	50.00%	1 Missing ⚠️
...metry.Exporter.Console/ConsoleLogRecordExporter.cs	50.00%	1 Missing ⚠️
...elemetry.Exporter.Console/ConsoleMetricExporter.cs	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7472      +/-   ##
==========================================
- Coverage   90.12%   90.11%   -0.02%     
==========================================
  Files         285      285              
  Lines       15343    15447     +104     
==========================================
+ Hits        13828    13920      +92     
- Misses       1515     1527      +12     

Flag	Coverage Δ
unittests-Project-Experimental	89.98% <91.66%> (-0.14%)	⬇️
unittests-Project-Stable	90.01% <91.66%> (-0.13%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
...ementation/Serializer/ProtobufOtlpLogSerializer.cs	98.52% <100.00%> (+0.02%)	⬆️
...ntation/Serializer/ProtobufOtlpMetricSerializer.cs	99.02% <100.00%> (+<0.01%)	⬆️
...entation/Serializer/ProtobufOtlpTraceSerializer.cs	95.07% <100.00%> (+0.03%)	⬆️
...nTelemetry/Internal/OpenTelemetrySdkEventSource.cs	67.34% <100.00%> (+0.33%)	⬆️
src/OpenTelemetry/Resources/Resource.cs	96.77% <100.00%> (+1.53%)	⬆️
...enTelemetry/Resources/ResourceBuilderExtensions.cs	100.00% <100.00%> (ø)
...emetry.Exporter.Console/ConsoleActivityExporter.cs	91.42% <50.00%> (-1.22%)	⬇️
...metry.Exporter.Console/ConsoleLogRecordExporter.cs	95.83% <50.00%> (-1.31%)	⬇️
...elemetry.Exporter.Console/ConsoleMetricExporter.cs	74.45% <50.00%> (-0.37%)	⬇️

... and 2 files with indirect coverage changes

[Copilot]

Pull request overview

This PR adds first-class support for a Resource Schema URL in the SDK layer, including correct merge behavior, and ensures the Schema URL is emitted by the console exporter and OTLP protobuf serializers.

Changes:

• Added Resource.SchemaUrl plus merge logic consistent with the spec (including a warning on conflicts).
• Added public ResourceBuilder.AddAttributes(..., schemaUrl) overload to allow contributors/detectors to supply a Schema URL.
• Propagated Schema URL to console output and OTLP Resource* messages, with unit + fuzz test coverage.

Reviewed changes

Copilot reviewed 19 out of 19 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/OpenTelemetry.Tests/Resources/ResourceTests.cs	Adds unit tests for Schema URL normalization and merge behavior (including conflict warning).
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.Tests/OtlpTraceExporterTests.cs	Verifies Schema URL flows through provider resource -> OTLP trace export request.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.FuzzTests/ProtobufOtlpTraceSerializerTests.cs	Adds fuzz/property test to ensure trace ResourceSpans Schema URL round-trips.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.FuzzTests/ProtobufOtlpMetricSerializerTests.cs	Adds fuzz/property test to ensure metric ResourceMetrics Schema URL round-trips.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.FuzzTests/ProtobufOtlpLogSerializerTests.cs	Adds fuzz/property test to ensure log ResourceLogs Schema URL round-trips.
test/OpenTelemetry.Exporter.OpenTelemetryProtocol.FuzzTests/Generators.cs	Extends resource generator to include Schema URL variants.
src/OpenTelemetry/Resources/ResourceBuilderExtensions.cs	Introduces AddAttributes(..., schemaUrl) public overload and docs.
src/OpenTelemetry/Resources/Resource.cs	Implements Schema URL storage, normalization, and merge logic with conflict warning.
src/OpenTelemetry/Internal/OpenTelemetrySdkEventSource.cs	Adds event for Schema URL merge conflict warning (EventId 59).
src/OpenTelemetry/CHANGELOG.md	Adds changelog entry for Resource Schema URL support.
src/OpenTelemetry/.publicApi/Stable/PublicAPI.Unshipped.txt	Tracks newly added stable public APIs (constructor, property, extension overload).
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpTraceSerializer.cs	Serializes ResourceSpans schema_url when present.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpMetricSerializer.cs	Serializes ResourceMetrics schema_url when present.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/Implementation/Serializer/ProtobufOtlpLogSerializer.cs	Serializes ResourceLogs schema_url when present.
src/OpenTelemetry.Exporter.OpenTelemetryProtocol/CHANGELOG.md	Adds OTLP exporter changelog entry for emitting Resource schema URL fields.
src/OpenTelemetry.Exporter.Console/ConsoleMetricExporter.cs	Prints Resource Schema URL alongside resource attributes for metrics.
src/OpenTelemetry.Exporter.Console/ConsoleLogRecordExporter.cs	Prints Resource Schema URL alongside resource attributes for logs.
src/OpenTelemetry.Exporter.Console/ConsoleActivityExporter.cs	Prints Resource Schema URL alongside resource attributes for traces/activities.
src/OpenTelemetry.Exporter.Console/CHANGELOG.md	Adds console exporter changelog entry for printing Resource Schema URL.

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[Kielek]

I think that we are missing one test case

        const string OldSchemaUrl = "https://opentelemetry.io/schemas/1.0.0";
        const string UpdatingSchemaUrl = "https://opentelemetry.io/schemas/1.1.0";
        const string UpdatingSchemaUr2l = "https://opentelemetry.io/schemas/1.2.0";


        var current = new Resource([], OldSchemaUrl);
        var updating = new Resource([], UpdatingSchemaUrl);
        var updating2 = new Resource([], UpdatingSchemaUrl2);

        var merged = current.Merge(updating).Merge(updating2;

		Assert.Null(merged.SchemaUrl);

I do not executed code, but I think it will leads to https://opentelemetry.io/schemas/1.2.0

[martincostello]

I've added a test that shows how it currently works.

[Kielek]

IMO it is bad, typically, you call.

.AddResource1()
.AddResource2()
.AddResource3()
.AddResource4()

Depends on the number of different schemaUrls it can lead to different schemarUrl

[martincostello]

How do we fix that without diverging from the spec?

If they're all different schema URLs every even-numbered resource will cause a conflict and the schema URL will be lost at the end, and every even-numbered resource will "win" because the previous merge lost.

We could do a first or last always wins the merge approach, but that would revert your original suggestion to return null.

[Kielek]

We can keep internal error state, (I think that the Go-lang is doing that). With this we will have consistent behavior.

[martincostello]

Latest change should do that now.

[Kielek]

LGTM, thanks!