Expose OpenTelemetry configuration settings in admin interface

[Copilot]

Administrators need control over OpenTelemetry instrumentation to manage Application Insights costs, comply with privacy requirements, and optimize telemetry collection across environments.

Changes

Configuration Settings (8 exposed)

• OTEL_SERVICE_NAME - Environment identification (e.g., simplechat-prod)
• OTEL_TRACES_SAMPLER - Sampling strategy (always_on, traceidratio, parentbased_*)
• OTEL_TRACES_SAMPLER_ARG - Sampling ratio (0.0-1.0, validated)
• OTEL_PYTHON_FLASK_EXCLUDED_URLS - Regex patterns for endpoint exclusion
• OTEL_PYTHON_DISABLED_INSTRUMENTATIONS - Selective instrumentation disable
• OTEL_LOGS_EXPORTER / OTEL_METRICS_EXPORTER - Export destinations
• Enable Live Metrics - Azure Monitor live stream toggle

Implementation

• functions_appinsights.py - Reads settings and applies as environment variables before configure_azure_monitor()
• route_frontend_admin_settings.py - Form handling with validation (sampler arg range check)
• admin_settings.html - New "OpenTelemetry Configuration" section with dropdowns and tooltips
• config.py - Version bump to 0.229.099

Documentation

• docs/features/OPENTELEMETRY_CONFIGURATION.md - Technical reference with use cases, cost optimization strategies
• docs/features/OPENTELEMETRY_QUICK_REFERENCE.md - Quick setup scenarios (production, dev, privacy-focused, external metrics)
• functional_tests/test_otel_settings.py - 8 tests covering validation, mappings, scenarios

Example Configurations

Production (90% cost reduction):

otel_traces_sampler: "parentbased_traceidratio"
otel_traces_sampler_arg: "0.1"  # 10% sampling
otel_flask_excluded_urls: "healthcheck,/health,/external/health"

Privacy-focused (no DB query capture):

otel_disabled_instrumentations: "sqlalchemy,pymysql,psycopg2"

Settings persist in Cosmos DB, applied at startup. Application restart required for changes to take effect.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Review Open Telemetry settings to expose in admin settings</issue_title>
<issue_description>Review for implementation OTEL settings for FlaskInstrumentator to expose via the admin app settings, why they might want/need to be exposed, use cases for exposing each setting, etc.

Ex: OTEL_PYTHON_DISABLED_INSTRUMENTATIONS</issue_description>

<agent_instructions>Review and propose settings to expose in admin app settings for open telemetry FlaskInstrumentator. Include definitions for why an admin would need it exposed, and why they may want to toggle it on or off. Include the default setting. </agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Review Open Telemetry settings to expose in admin settings #563

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