Python: Updates to user agent. Add unit tests.

[moonbox3]

Motivation and Context

Updates to the User-Agent are required so that we can align with all three SK languages. Examples:

User agent

• semantic-kernel-csharp/1.1.1 [existing user agent]
• semantic-kernel-java/1.1.1 [existing user agent]
• semantic-kernel-python/1.1.1 [existing user agent]

semantic-kernel-version header

• csharp/1.1.1
• java/1.1.1
• python/1.1.1

Description

Updates to the user agent to reflect the desired changes/standardization across all SK languages. Adding unit tests.

• Closes Python: Update User-Agent to align with other SK languages #6827
• Moves the USER_AGENT const from its previous home in the openai const file to a more generic const file.
• Updates unit tests to be able to run properly when a valid .env file exists in the current working directory. The unit tests patch the env vars and our current implementation of Pydantic Settings loads the .env file if not specified.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

[markwallace-microsoft]

Python 3.10 Test Coverage Report •

File	Stmts	Miss	Cover	Missing
semantic_kernel/connectors
telemetry.py	15	2	87%	17–18
semantic_kernel/connectors/ai/open_ai/services
azure_config_base.py	34	4	88%	75–77, 92
open_ai_config_base.py	32	1	97%	58
semantic_kernel/connectors/openapi_plugin
openapi_runner.py	99	64	35%	51–53, 59–60, 66–80, 84–100, 104–106, 110–112, 115–118, 127–169
TOTAL	6532	756	88%

Python 3.10 Unit Test Overview

Tests	Skipped	Failures	Errors	Time
1526	1 💤	0 ❌	0 🔥	25.468s ⏱️