Rework Docker support

- Use multi-stage build for the application image
- Utilize connection pool init timeout for waiting on database container startup,
"docker-compose-wait" dependency is no longer required
- Override database host through environment variable - used in docker-compose
- Rename database scripts for explicit ordering (db container loads them alphabetically)

src/main/java/tools/DatabaseConnection.java

@@ -27,10 +27,19 @@ public class DatabaseConnection {
         return dataSource.getConnection();
     }
 
+    private static String getDbUrl() {
+        // Environment variables override what's defined in the config file
+        // This feature is used for the Docker support
+        String hostOverride = System.getenv("DB_HOST");
+        String host = hostOverride != null ? hostOverride : YamlConfig.config.server.DB_HOST;
+        String dbUrl = String.format(YamlConfig.config.server.DB_URL_FORMAT, host);
+        return dbUrl;
+    }
+
     private static HikariConfig getConfig() {
         HikariConfig config = new HikariConfig();
 
-        config.setJdbcUrl(YamlConfig.config.server.DB_URL);
+        config.setJdbcUrl(getDbUrl());
         config.setUsername(YamlConfig.config.server.DB_USER);
         config.setPassword(YamlConfig.config.server.DB_PASS);