Migrate to maven (#61)

## Description

This will fix #3 

Also incrementing the version by one, and moving from `de.stackable` prefix to `tech.stackable` prefix.

Test run: https://ci.stackable.tech/view/02%20Operator%20Tests%20(custom)/job/druid-operator-it-custom/40/

The test uses a custom image that includes this new version of the plugin

.github/workflows/gradle.yml → .github/workflows/maven.yml

@@ -1,7 +1,7 @@
 # This workflow will build a Java project with Maven, and cache/restore any dependencies to improve the workflow execution time
 # For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
 ---
-name: Java CI with Gradle
+name: Java CI with Maven
 
 on:
   push:
@@ -22,11 +22,11 @@ jobs:
         with:
           java-version: '11'
           distribution: 'adopt'
-          cache: gradle
+          cache: maven
       - name: Set up OpenPolicyAgent
         run: |
-          curl -L -o opa https://openpolicyagent.org/downloads/v0.33.1/opa_linux_amd64_static
+          curl -L -o opa https://openpolicyagent.org/downloads/v0.46.1/opa_linux_amd64_static
           chmod +x opa
           sudo mv opa /usr/local/bin/opa
-      - name: Build with Gradle
-        run: ./gradlew build
+      - name: Build with Maven
+        run: mvn -B package

.gitignore

@@ -4,4 +4,6 @@
 # Ignore Gradle build output directory
 build
 
-.idea
+.idea
+
+target

CHANGELOG.md

@@ -2,6 +2,13 @@
 
 ## [Unreleased]
 
+## Changed
+
+- Changed build system to Maven ([#61]).
+- Changed module prefix from `de` to `tech` ([#61]).
+
+[#61]: https://github.com/stackabletech/druid-opa-authorizer/pull/61
+
 ## [0.3.0] - 2022-10-13
 
 ## Changed

README.md

@@ -3,15 +3,11 @@
 A Druid extension to request policy decisions from the [Open Policy Agent](https://www.openpolicyagent.org/) (OPA).
 
 ## Building
-Simply building the library:
+This repository uses maven:
 
-    ./gradlew build
+  mvn package
 
-To build a zip that's easy to use with Druid use:
-
-    ./gradlew distZip
-
-The zip still has to be modified a bit, all the jars should be at the top level. At the moment this needs to be done by hand.
+The packaged zip plugin is located at `target/druid-opa-authorizer-0.3.0.zip`.
 
 ## Installing
 Build the distribution (zip with all the dependencies) and put it all in the extensions directory.