docs: Add security policy for logging sensitive telemetry data

Author: Arunodoy18

.chloggen/add-sensitive-data-logging-policy.yaml

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+change_type: enhancement
+component: docs
+note: Add security policy for logging sensitive telemetry data.
+issues: [14431]

docs/security/logging.md

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+# Logging Policy for Sensitive Data
+
+To ensure the security and privacy of data processed by the OpenTelemetry Collector, the following rules regarding logging must be observed.
+
+## Rules
+
+1. **No Sensitive Data at Info/Warn/Error Levels**
+   - Telemetry data (metric names, label values, attribute values, resource attributes) must NOT be logged at `Info`, `Warn`, or `Error` levels.
+   - PII (Personally Identifiable Information), credentials, and exact payload contents are strictly prohibited in high-level logs.
+
+2. **Error Messages**
+   - Returned errors must be generic and actionable without embedding specific metric data.
+   - Do NOT wrap errors with formatted strings containing raw telemetry values (e.g., `fmt.Errorf("failed processing metric %s: %w", metricName, err)` is prohibited).
+   - Use structural logging fields at `Debug` level if context is needed.
+
+3. **Debug Level Exception**
+   - Detailed diagnostic context, including specific metric names or attribute values, MAY be logged at `Debug` level only.
+   - This allows operators to opt-in to verbose logging for troubleshooting without polluting default logs with potentially sensitive data.
+
+## Implementation Guidelines
+
+**Incorrect:**
+```go
+// BAD: Leaks sensitive metric name in error
+if err := process(metric); err != nil {
+    return fmt.Errorf("failed to process metric %s: %w", metric.Name(), err)
+}
+```
+
+**Correct:**
+```go
+// GOOD: Logs details at debug, returns generic error
+if err := process(metric); err != nil {
+    logger.Debug("failed to process metric",
+        zap.String("metric_name", metric.Name()),
+        zap.Error(err))
+    return fmt.Errorf("failed to process metric: %w", err)
+}
+```