Add Gradle plugin to generate uber JAR

Add Jon Regelmnan's Gradle plugin [shadow][1] to introduce the task
`shadowJar` that will generate an [uber JAR][2] that contains all
dependencies required to run the application.

[Configure shadow][3] to create a JAR file named `galaxy-raiders.jar`.

Update the README.md to use a lighter container (Eclipse Temujin
rather than Gradle) to run the project in production mode.

[1]: https://github.com/johnrengelman/shadow
[2]: https://stackoverflow.com/questions/11947037/what-is-an-uber-jar
[3]: https://imperceptiblethoughts.com/shadow/configuration/#configuring-output-name

README.md

@@ -40,9 +40,9 @@ To compile all classes in the project, run:
 docker container run --rm --user gradle --volume "$PWD":/home/gradle/app --workdir /home/gradle/app gradle:7.4.2-jdk17 gradle --no-daemon clean assemble
 ```
 
-To generate a runnable JAR of the project, run:
+To generate a runnable self-contained JAR of the project, run:
 ```bash
-docker container run --rm --user gradle --volume "$PWD":/home/gradle/app --workdir /home/gradle/app gradle:7.4.2-jdk17 gradle --no-daemon clean jar
+docker container run --rm --user gradle --volume "$PWD":/home/gradle/app --workdir /home/gradle/app gradle:7.4.2-jdk17 gradle --no-daemon clean shadowJar
 ```
 
 ## Tests
@@ -61,9 +61,10 @@ To execute the project in development mode (with live reload), run:
 docker container run --rm --user gradle --volume "$PWD":/home/gradle/app --workdir /home/gradle/app gradle:7.4.2-jdk17 gradle --continuous run
 ```
 
-To execute the project in production mode, generate a runnable JAR, then run:
+To execute the project in production mode, generate a runnable self-contained
+JAR of the project, then run:
 ```bash
-docker container run --rm --user gradle --volume "$PWD":/home/gradle/app --workdir /home/gradle/app gradle:7.4.2-jdk17 java -jar ./app/build/libs/app.jar
+docker container run --rm --volume "$PWD"/app/build/libs/galaxy-raiders.jar:/bin/runner/galaxy-raiders.jar --workdir /bin/runner eclipse-temurin:17-jdk java -jar galaxy-raiders.jar
 ```
 
 ## Other tasks

app/build.gradle.kts

@@ -24,6 +24,9 @@ plugins {
   // Apply the Test Logger plugin to print test results in the test task.
   id("com.adarshr.test-logger") version "3.2.0"
 
+  // Apply the Shadow JAR Plugin to generate a standalone uber Jar.
+  id("com.github.johnrengelman.shadow") version "7.1.2"
+
   // Apply the Kover plugin to better support Kotlin code coverage.
   id("org.jetbrains.kotlinx.kover") version "0.5.0"
 
@@ -79,3 +82,16 @@ tasks.test {
 tasks.jacocoTestReport {
     dependsOn(tasks.test)
 }
+
+// Configure the metadata to generate an uber JAR.
+tasks.shadowJar {
+  archiveBaseName.set("galaxy-raiders")
+  archiveVersion.set("")
+  archiveClassifier.set("")
+}
+
+// Configure Gradle to send its stdin to the program.
+// https://stackoverflow.com/questions/13172137/console-application-with-java-and-gradle
+tasks.getByName("runShadow", JavaExec::class) {
+  standardInput = System.`in`
+}