[lesnik512]

Closes #320.

service_name and service_version now default to None instead of "micro-service" and "1.0.0".

• OpenTelemetry: an unset name or version stays out of the resource, so the SDK takes it from OTEL_SERVICE_NAME and OTEL_RESOURCE_ATTRIBUTES. With neither set, the name is unknown_service. _build_resource already dropped empty values, so it needed no change.
• Sentry: a service_version that is set goes to sentry_sdk.init as release. An unset one adds no release key, and sentry-sdk falls back to SENTRY_RELEASE, the git revision or CI variables, as before. sentry_additional_params can still override it.

Some readers need a string: FastAPI's title and version, Litestar's OpenAPI title and version, Litestar's Prometheus app_name, the health-check body, and Pyroscope's application_name. They read two new BaseConfig properties, service_name_or_default and service_version_or_default, which fall back to the old strings. You chose that, so for these readers nothing changes from 1.x. The issue's breaking-change list assumed they would get a new fallback.

Tests

Written first. These failed on main:

• test_opentelemetry_service_name_falls_back_to_otel_service_name[config0-from-env]: with OTEL_SERVICE_NAME set and a default config, the resource had micro-service. This was test_opentelemetry_configured_service_name_wins_over_env. I renamed it because the default case now expects the variable's value. The configured cases are unchanged.
• test_opentelemetry_service_version_falls_back_to_otel_resource_attributes[None-from-env]: OTEL_RESOURCE_ATTRIBUTES=service.version=... was overridden by 1.0.0.
• test_sentry_release_follows_service_version[service-version] and [service-version-wins-over-env]: no release was passed.
• test_service_name_and_version_fall_back_for_readers_that_need_a_string: the properties are new.
• test_from_object_skips_missing_attribute and test_from_dict_drops_unknown_keys_silently: they assert the defaults, which are now None.

test_sentry_release_follows_service_version[env-when-unset] covers SENTRY_RELEASE with a default config. It passed on main and still does.

These pin the fallback for the string readers and passed on main too: test_built_app_title_and_version_fall_back_when_unset (FastAPI), test_litestar_openapi_and_prometheus_fall_back_to_default_service_name, and test_pyroscope_application_name_falls_back_when_service_name_unset. The health-check body was already covered by test_healthchecks_render_data_default.

test_from_object_skips_none_attribute and test_from_dict_explicit_none_overrides_default used service_name to show that None is skipped or overrides a default. Once the default is None they could no longer tell the difference, so they use service_debug now.

The full suite passes, 588 tests at 100% coverage (just test-ci). just lint (including ty), just adr-check and just docs-build pass too. No floor changes.

Docs

configuration.md has a new "Service name and version" section covering what each backend does when the fields are unset. The Sentry section links to it. The resource paragraph that said OTEL_SERVICE_NAME gets overridden is replaced.

Breaking changes

• If you never set service_name, service.name now comes from OTEL_SERVICE_NAME where it is set, and is unknown_service otherwise. Before, it was micro-service.
• If you never set service_version, service.version is gone from the resource unless OTEL_RESOURCE_ATTRIBUTES sets it.
• If you set service_version, Sentry now gets it as the release, in place of the one sentry-sdk would pick, including SENTRY_RELEASE.
• Code that reads config.service_name or config.service_version can now get None. Use service_name_or_default and service_version_or_default for the old values.