opentelemetry-sdk: align resource detector schema url conflict behavor with other languages

[herin049]

Description

This PR is related to the discussion in the 9/17/26 SIG call regarding handling merging of Resource objects with conflicting schema URLs. The behavior prior to this PR is to drop all attributes for new Resources while merging if the new Resource's schema URL is incompatible with the current Resource's schema URL. This PR updates the SDK's internal resource detector schema URL conflict behavior with other languages. That is, it simply logs a warning and permanently clears the schema URL.

Related to: #2688

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

uv run tox -e py314-test-opentelemetry-sdk

Does This PR Require a Contrib Repo Change?

• Yes. - Link to PR:
• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

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Waiting on reviewers · refreshed 2026-09-23 16:00 UTC

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[JoeyPatricio]

Read through the merge logic and the tests. Behavior matches what Java and Go do on conflict (attributes merged, warning, schema_url cleared), with the addition that the cleared state is kept through later merges, which the description calls out. Test cases cover the conflict, the sticky case, and the aggregated-resources path. LGTM.

[Copilot]

Copilot review overview

🟡 Changes recommended

Equality and hashing omit behaviorally significant conflict state, and the central attribute-merging behavior lacks an independent test.

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Review effort: Balanced
Findings: 1 · 2

Open (3)

• Include conflict state in equality and hashing · New
• Fix changelog typo to “behavior” · New
• Test attribute preservation during schema conflicts · New

What changed in this PR

Updates resource merging to retain attributes while permanently clearing conflicting schema URLs.

Changes:

• Tracks schema URL conflicts across merges.
• Logs conflicts as warnings and expands tests.
• Adds a changelog entry.

File	Description
resources/​__init__.py	Implements conflict-aware merging.
test_resources.py	Updates merge tests.
.changelog/​5672.added	Documents the behavior change.

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