Add Micrometer Observability documentation

Closes gh-32833
Closes gh-32912

spring-boot-project/spring-boot-docs/src/main/java/org/springframework/boot/docs/actuator/observability/MyCustomObservation.java

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2012-2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.docs.actuator.observability;
+
+import io.micrometer.observation.Observation;
+import io.micrometer.observation.ObservationRegistry;
+
+import org.springframework.stereotype.Component;
+
+@Component
+public class MyCustomObservation {
+
+	private final ObservationRegistry observationRegistry;
+
+	public MyCustomObservation(ObservationRegistry observationRegistry) {
+		this.observationRegistry = observationRegistry;
+	}
+
+	public void doSomething() {
+		// @formatter:off
+		Observation.createNotStarted("doSomething", this.observationRegistry)
+				.lowCardinalityKeyValue("locale", "en-US")
+				.highCardinalityKeyValue("userId", "42")
+				.observe(() -> {
+					// Execute business logic here
+				});
+		// @formatter:on
+	}
+
+}