BAEL-4652: Running Spring Boot with PostgreSQL in Docker Compose (#10255)

* Initial commit after Spring Starter Wizard.

* Shortened class names.

* Added Docker files, probably not working, yet.

* Ignoring JAR files.

* Docker files work now.

* Fixed application start-up.

* Creating & querying customer.

* Simplified by removing "files" sub-folder for applicaton JAR file.

* Removed more unnecessary settings.

* Removed last "application.properties" setting since this is part of
the Docker Compose file.

* Final tweaking.

docker/docker-spring-boot-postgres/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.boot</groupId>
+		<artifactId>spring-boot-starter-parent</artifactId>
+		<version>2.4.0</version>
+		<relativePath/> <!-- lookup parent from repository -->
+	</parent>
+	<groupId>com.baeldung.docker</groupId>
+	<artifactId>spring-boot-postgres-docker</artifactId>
+	<version>0.0.1-SNAPSHOT</version>
+	<name>spring-boot-postgres-docker</name>
+	<description>Demo project showing Spring Boot, PostgreSQL, and Docker</description>
+
+	<properties>
+		<java.version>11</java.version>
+	</properties>
+
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-data-jpa</artifactId>
+		</dependency>
+
+		<dependency>
+			<groupId>org.postgresql</groupId>
+			<artifactId>postgresql</artifactId>
+			<scope>runtime</scope>
+		</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>