Implement PoC of MeasurementProcessor proposal

[Blinkuu]

Description

This PR is a Proof of Concept of the MeasurementProcessor concept for the OpenTelemetry Python SDK, following the design specified in OpenTelemetry Specification PR #4318.

MeasurementProcessor enables powerful measurement processing capabilities including:

• Dynamic attribute injection from OpenTelemetry Baggage for end-to-end telemetry correlation
• Attribute filtering to remove sensitive data
• Measurement dropping based on value ranges or other criteria
• Measurement modification for unit conversion, value transformation, etc.
• And more...

The implementation uses a chain-of-responsibility pattern where each processor decides whether to pass, modify, or drop measurements by calling (or not calling) the next processor in the chain.

Key components added:

• MeasurementProcessor abstract interface
• MeasurementProcessorChain for managing processor execution
• Integration with existing MeterProvider, SdkConfiguration, and MeasurementConsumer
• Example processor implementations (BaggageMeasurementProcessor, StaticAttributeMeasurementProcessor, etc.)

Usage:

from opentelemetry.sdk.metrics import MeterProvider
from opentelemetry.sdk.metrics._internal.measurement_processor import (
    BaggageMeasurementProcessor,
    ValueRangeMeasurementProcessor,
)

processors = [
    BaggageMeasurementProcessor(),  # Add baggage as attributes
    ValueRangeMeasurementProcessor(min_value=0),  # Drop negative values
]

meter_provider = MeterProvider(measurement_processors=processors)

Type of change

Please delete options that are not relevant.

• [x] New feature (non-breaking change which adds functionality)
• [x] This change requires a documentation update

How Has This Been Tested?

I'm not a Python expert, and this is just a PoC. Therefore, no extensive testing has been conducted.

There are some tests that can be run with the following bash command:

python -m unittest opentelemetry-sdk/tests/metrics/test_measurement_processor.py -v

You can also see and run the example:

uv sync
source .venv/bin/activat
cd docs/examples/metrics/measurement-processors/
python measurement_processors.py

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