add javadoc warning

Author: ldetmer

java-bigquery/google-cloud-bigquery/src/main/java/com/google/cloud/bigquery/BigQueryOptions.java

@@ -126,7 +126,18 @@ public Builder setDataFormatOptions(DataFormatOptions dataFormatOptions) {
     /**
      * Enables OpenTelemetry tracing functionality for this BigQuery instance
      *
-     * <p>[TODO] add warning text here
+     * <p><div class="warning"> Traces may contain sensitive data such as resource names, full URLs,
+     * and error messages.
+     *
+     * <p>Before configuring subscribers or exporters for traces, review the contents of the spans
+     * and consult the <a
+     * href="https://opentelemetry.io/docs/security/handling-sensitive-data/">OpenTelemetry
+     * documentation</a> to set up filters and formatters to prevent leaking sensitive information,
+     * depending on your intended use case.
+     *
+     * <p>See also: <a
+     * href="https://opentelemetry.io/docs/concepts/semantic-conventions/">OpenTelemetry Semantic
+     * Conventions</a> </div>
      *
      * @param enableOpenTelemetryTracing enables OpenTelemetry tracing if true
      */
@@ -138,6 +149,19 @@ public Builder setEnableOpenTelemetryTracing(boolean enableOpenTelemetryTracing)
     /**
      * Sets the OpenTelemetry tracer for this BigQuery instance to be tracer.
      *
+     * <p><div class="warning"> Traces may contain sensitive data such as resource names, full URLs,
+     * and error messages.
+     *
+     * <p>Before configuring subscribers or exporters for traces, review the contents of the spans
+     * and consult the <a
+     * href="https://opentelemetry.io/docs/security/handling-sensitive-data/">OpenTelemetry
+     * documentation</a> to set up filters and formatters to prevent leaking sensitive information,
+     * depending on your intended use case.
+     *
+     * <p>See also: <a
+     * href="https://opentelemetry.io/docs/concepts/semantic-conventions/">OpenTelemetry Semantic
+     * Conventions</a> </div>
+     *
      * @param tracer OpenTelemetry tracer to be used
      */
     public Builder setOpenTelemetryTracer(Tracer tracer) {