Add Micrometer Tracing to sample apps (#160)

Also documents how to configure Micrometer Observations.

See #147

spring-pulsar-sample-apps/build.gradle

@@ -8,6 +8,12 @@ description = 'Spring Pulsar Sample Applications'
 dependencies {
 	api project(':spring-pulsar-spring-boot-starter')
 	implementation 'com.google.code.findbugs:jsr305'
+
+	// observability
+	implementation 'org.springframework.boot:spring-boot-starter-actuator'
+	implementation 'io.micrometer:micrometer-tracing-bridge-brave'
+	implementation 'io.zipkin.reporter2:zipkin-reporter-brave'
+	implementation 'io.zipkin.reporter2:zipkin-sender-urlconnection'
 }
 
 springBoot {

spring-pulsar-sample-apps/src/main/resources/application.yml

@@ -1,3 +1,10 @@
 logging:
   level:
     org.apache.pulsar: error
+
+management:
+  tracing:
+    enabled: false
+  zipkin:
+    tracing:
+      endpoint: "http://localhost:9411/api/v2/spans"