opentelemetry-util-genai: Align message-part class names with semconv (*Part suffix) (Util changes)

[rads-1996]

Description

Complies with the semantic conventions for non-normative models. (util changes)

Type of change

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• 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?

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instructions so we can reproduce. List any relevant details for your test
configuration.

• All test suites have been run

Checklist

See CONTRIBUTING.md
for the style guide, changelog guidance, and more.

• Followed the style guidelines of this project
• Changelog updated if the change requires an entry
• Unit tests added
• Documentation updated

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[Copilot]

Pull request overview

Updates opentelemetry-util-genai message-part model naming to align with the GenAI semconv non-normative Python models (using *Part suffixes), while keeping backwards-compatible access to the pre-*Part names.

Changes:

• Renamed message-part dataclasses in types.py to *Part names and updated the MessagePart union accordingly.
• Updated util tests and upload-related logic to use the new *Part names; added tests asserting the legacy names still resolve.
• Updated util README wording and added Towncrier fragments describing the change + deprecations.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
util/opentelemetry-util-genai/src/opentelemetry/util/genai/types.py	Renames message-part classes to *Part, updates MessagePart, and adds legacy-name aliases.
util/opentelemetry-util-genai/src/opentelemetry/util/genai/_upload/completion_hook.py	Updates hashability check to use TextPart.
util/opentelemetry-util-genai/src/opentelemetry/util/genai/_tool_invocation.py	Updates docstring to refer to ToolCallRequestPart for message parts.
util/opentelemetry-util-genai/tests/test_utils.py	Switches helpers to TextPart and adds tests for legacy alias behavior.
util/opentelemetry-util-genai/tests/test_toolcall.py	Updates tests to *Part tool-call types and adds alias-compat tests.
util/opentelemetry-util-genai/tests/test_upload.py	Updates upload hook tests to use TextPart and *Part tool-call message parts.
util/opentelemetry-util-genai/tests/test_workflow_invocation.py	Updates workflow invocation tests to use TextPart.
util/opentelemetry-util-genai/tests/test_handler_workflow.py	Updates handler workflow tests to use TextPart.
util/opentelemetry-util-genai/tests/test_handler_fetch_response.py	Updates handler fetch-response test data to use TextPart.
util/opentelemetry-util-genai/tests/test_handler_completion_hook.py	Updates completion-hook tests to use TextPart.
util/opentelemetry-util-genai/tests/test_handler_agent.py	Updates agent handler tests to use TextPart.
util/opentelemetry-util-genai/README.rst	Updates README terminology to reference *Part message types.
util/opentelemetry-util-genai/.changelog/450.changed	Towncrier fragment for the naming alignment.
util/opentelemetry-util-genai/.changelog/450.deprecated	Towncrier fragment documenting the deprecation of legacy names.

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[aabmass]

All these deprecated notices and extra classes looks like a lot of tech debt to take on for an experimental package.

Is there a strong reason to align with the non-normative conventions? We could even update the non-normative conventions to match the names in this util. WDYT?

[rads-1996]

@aabmass The initial discussion for this change started in another PR -

Following Liudmila's remark, I went and checked that for some data classes we were following the non-normative semantic conventions and for some we weren't.

Even if we move with the suggestion of modifying the semantic conventions, we will still have to provide backward compatibility for the classes which already included the *Part suffix such as GenericPart, CompactionPart. Unless we don't mind some classes having the *Part suffix and others not.