Explain Spring Boot Metrics and Micrometer.

Micrometer provides metrics collection:\n\n@RestController\npublic class MetricsController {\n private final Counter requestCounter;\n private final Timer requestTimer;\n \n public MetricsController(MeterRegistry meterRegistry) {\n this.requestCounter = Counter.builder("api.requests")\n .description("API request count")\n .register(meterRegistry);\n this.requestTimer = Timer.builder("api.request.duration")\n .register(meterRegistry);\n }\n \n @GetMapping("/api/data")\n public String getData() {\n return Timer.Sample.start(requestTimer)\n .stop(requestTimer);\n }\n}