Identical Java source (env-var-proof/OtelEnvProofApplication.java), compiled twice against two
different spring-boot-starter-parent versions -- 4.0.8 and 4.1.1 -- run with ONLY standard OTEL_*
environment variables set (zero management.otlp.* Spring properties anywhere), against a
minimal stand-in OTLP receiver that just logs every POST it gets:

  OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:PORT
  OTEL_METRIC_EXPORT_INTERVAL=2000

--- Spring Boot 4.1.1 ---

  Publishing metrics for OtlpMeterRegistry every 2s to http://localhost:PORT/v1/metrics ...

  receiver log (20s window):
  ... POST /v1/metrics content-length=8247   (x11, one every ~2s)

  Both the endpoint AND the interval standard env vars were honored.

--- Spring Boot 4.0.8, same two env vars ---

  Publishing metrics for OtlpMeterRegistry every 1m to http://localhost:PORT/v1/metrics ...

  receiver log (20s window):
  ... POST /v1/metrics content-length=8247   (x1, at JVM shutdown only)

  The endpoint env var was honored (Micrometer's own OtlpConfig has long fallen back to
  OTEL_EXPORTER_OTLP_ENDPOINT independent of Spring Boot's own property binding). The interval
  env var was NOT -- the exporter still logs "every 1m", the JVM's own default, and the only POST
  the receiver saw was the one every PushMeterRegistry fires on shutdown regardless of interval.

--- Spring Boot 4.0.8, old-style Spring property instead ---

  MANAGEMENT_OTLP_METRICS_EXPORT_URL=http://localhost:PORT/v1/metrics
  MANAGEMENT_OTLP_METRICS_EXPORT_STEP=2s

  Publishing metrics for OtlpMeterRegistry every 2s to http://localhost:PORT/v1/metrics ...

  receiver log (20s window):
  ... POST /v1/metrics content-length=8435   (x11, one every ~2s)

  Boot 4.0's own management.otlp.* properties always worked for this. What's new in 4.1 is that
  the SAME standard OTEL_* variable now works too, without a Spring-specific property to learn --
  useful the moment the same env vars are already used to configure something else in the same
  deployment (the OTel Collector, another language's service, docker-compose.yml).