Replace java:8 by eclipse-temurin:8, so this works with recent docker installations

[DaGeRe]

java:8 is not longer a Docker image, instead, the concrete JVM (e.g., eclipse-temurin:8) should be specified. Using java:8 results in errors like

[ERROR] Failed to execute goal com.spotify:docker-maven-plugin:0.4.9:build (default-cli) on project query-side-blog-service: Exception caught: manifest for java:8 not found: manifest unknown: manifest unknown -> [Help 1]

I've replaced all FROM specification in the dockerfiles, so after this is fixed, the project should build again with recent docker versions.

This can be done using for file in $(find . -name "Dockerfile"); do sed -i "s/java:8/eclipse-temurin:8/g" $file; done (or potentially another image, like the slim version of temurin).