Update Dockerfile

Updated comments.

Dockerfile

@@ -23,16 +23,13 @@ RUN ./mvnw clean install -DskipTests
 # The base image to package. This is a multi-stage build using a new context. 
 FROM eclipse-temurin:21-jdk-jammy
 
-# Setup a non-root user with user privileges instead of root privileges. 
-# RUN adduser -D myuser
-# RUN addgroup usergroup; adduser --ingroup usergroup --disabled-password myuser; 
-
 # Install PostgreSQL and change PostgreSQL authentication to trust. 
-# Install the PostgreSQL package.
+# Install the PostgreSQL package. 
 RUN apt-get update && apt-get install -y postgresql
 
+# As a security best practice, switch to a non-root user with user privileges instead of root privileges. 
 # The USER Dockerfile instruction sets the preferred user name (or UID) and optionally the user group (or GID) while running the image — and for any subsequent RUN, CMD, or ENTRYPOINT instructions. 
-# Change the user to the PostgreSQL user.
+# Change the user to the PostgreSQL user. 
 USER postgres
 
 # Start the PostgreSQL service and create a new database used by the application, then change the PostgreSQL authentication method to trust and restart the PostgreSQL service. 
@@ -55,10 +52,10 @@ EXPOSE $PORT
 # Copy the Jar file generated from the builder context into the Docker image. 
 # Docker uses caching to speed up builds by reusing layers from previous builds. 
 # To take advantage of caching, you should order your Dockerfile instructions so that the ones that change frequently are placed towards the end of the file. 
-# For example, if you’re copying files into the image, you should do that at the end of the Dockerfile.
+# For example, if you’re copying files into the image, you should do that at the end of the Dockerfile. 
 COPY --from=builder /opt/app/target/*.jar /opt/app/*.jar
 
 # Set the default command to run the Java application. 
 # The ENTRYPOINT instruction specifies the command that should be run. The CMD instruction provides default arguments to the ENTRYPOINT command. 
-# Start the PostgreSQL service, wait for it to start, then run the Java application via its Jar file. 
+# Start the PostgreSQL service, then wait for it to start by checking with pg_isready (a utility specifically designed for checking if PostgreSQL is ready to accept connections). Once started, run the Java application via its Jar file. 
 ENTRYPOINT service postgresql start && while ! pg_isready -h localhost -p 5432; do sleep 1; done && java -jar /opt/app/*.jar