feat: sap.service.display_name in telemetry

[LucasAlvesSoares]

Description

Adds sap.service.display_name as a new optional resource attribute in the SDK's OpenTelemetry telemetry configuration. The attribute is read from the SAP_SERVICE_DISPLAY_NAME environment variable and
follows the same pattern as sap.ord.id and mlflow.experiment_id — omitted entirely from the resource when the variable is unset or empty, so no placeholder noise is emitted.

Changes:

• Added ATTR_SAP_SERVICE_DISPLAY_NAME = "sap.service.display_name" constant
• Added ENV_SERVICE_DISPLAY_NAME = "SAP_SERVICE_DISPLAY_NAME" env var
• Wired the attribute into create_resource_attributes_from_env()
• Added unit tests covering unset, empty, set, and independence from other optional attributes

Type of Change

• New feature (non-breaking change that adds functionality)

How to Test

1. Set SAP_SERVICE_DISPLAY_NAME=My Service in your environment
2. Initialize the SDK with telemetry enabled
3. Observe that spans carry the resource attribute sap.service.display_name = "My Service"
4. Without the env var set, confirm the attribute is absent from the resource