Generate proper meta-data

To avoid that the app.* keys are shown as unknown in the editor, we can
enable the annotation processor.

Spring Boot metadata annotation processor looks for
`@ConfigurationProperties` bean on class and `@Bean` definition. For the
latter it exposes the properties found on the return type of the method.

Previously, we exposed `javax.sql.DataSource` that does not expose any
property (getter/setter) so the meta-data for that is empty. We switched
to the Tomcat connection pool to expose its relevant properties.

pom.xml

@@ -38,6 +38,12 @@
 			<scope>runtime</scope>
 		</dependency>
 
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-configuration-processor</artifactId>
+			<optional>true</optional>
+		</dependency>
+
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>

src/main/java/demo/customer/CustomerConfig.java

@@ -1,9 +1,9 @@
 package demo.customer;
 
 import javax.persistence.EntityManagerFactory;
-import javax.sql.DataSource;
 
 import demo.customer.domain.Customer;
+import org.apache.tomcat.jdbc.pool.DataSource;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
@@ -41,7 +41,7 @@ public JpaProperties customerJpaProperties() {
 	@Primary
 	@ConfigurationProperties(prefix = "app.customer.datasource")
 	public DataSource customerDataSource() {
-		return DataSourceBuilder.create().build();
+		return (DataSource) DataSourceBuilder.create().type(DataSource.class).build();
 	}
 
 	@Bean

src/main/java/demo/order/OrderConfig.java

@@ -1,9 +1,9 @@
 package demo.order;
 
 import javax.persistence.EntityManagerFactory;
-import javax.sql.DataSource;
 
 import demo.order.domain.Order;
+import org.apache.tomcat.jdbc.pool.DataSource;
 
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
@@ -39,7 +39,7 @@ public JpaProperties orderJpaProperties() {
 	@Bean
 	@ConfigurationProperties(prefix = "app.order.datasource")
 	public DataSource orderDataSource() {
-		return DataSourceBuilder.create().build();
+		return (DataSource) DataSourceBuilder.create().type(DataSource.class).build();
 	}
 
 	@Bean