Add the scheduling module

Three replicas of one application against one PostgreSQL database, proving
duplicate @Scheduled execution and then removing it with ShedLock: 24
executions where 8 were due, then 7 for 7 ticks.

Also measured: @SchedulerLock without @EnableSchedulerLock does nothing and
warns about nothing; spring.task.scheduling.pool.size=1 does not starve a
fixedRate job but delays it and fires 35 of 40 executions in a burst; and a
node whose clock is 40 seconds fast takes a live lock unless the provider
uses usingDbTime().

scheduling/pom.xml

@@ -0,0 +1,68 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0">
+  <modelVersion>4.0.0</modelVersion>
+
+  <parent>
+    <groupId>org.springframework.boot</groupId>
+    <artifactId>spring-boot-starter-parent</artifactId>
+    <version>4.1.1</version>
+    <relativePath/>
+  </parent>
+
+  <groupId>com.ankurm</groupId>
+  <artifactId>scheduling</artifactId>
+  <version>1.0</version>
+  <packaging>jar</packaging>
+
+  <properties>
+    <java.version>25</java.version>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    <!-- ShedLock is NOT managed by spring-boot-dependencies, so this version is pinned here.
+         7.9.0 was read from maven-metadata.xml on Maven Central; its jars are compiled for
+         Java 17 (MANIFEST Java-Version: 17, class file major version 61). -->
+    <shedlock.version>7.9.0</shedlock.version>
+  </properties>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter</artifactId>
+    </dependency>
+    <!-- spring-boot-starter-jdbc, not a bare spring-jdbc dependency: in Boot 4 the DataSource
+         and JdbcTemplate auto-configuration lives in the spring-boot-jdbc module, which the
+         starter brings and spring-jdbc does not. -->
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-jdbc</artifactId>
+    </dependency>
+    <dependency>
+      <groupId>org.postgresql</groupId>
+      <artifactId>postgresql</artifactId>
+    </dependency>
+
+    <dependency>
+      <groupId>net.javacrumbs.shedlock</groupId>
+      <artifactId>shedlock-spring</artifactId>
+      <version>${shedlock.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>net.javacrumbs.shedlock</groupId>
+      <artifactId>shedlock-provider-jdbc-template</artifactId>
+      <version>${shedlock.version}</version>
+    </dependency>
+
+    <dependency>
+      <groupId>org.springframework.boot</groupId>
+      <artifactId>spring-boot-starter-test</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+  <build>
+    <plugins>
+      <plugin>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-maven-plugin</artifactId>
+      </plugin>
+    </plugins>
+  </build>
+</project>