chore: test in java 17 and 21 (#32)

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## Description
<!-- Provide a detailed description of the changes -->

Runs tests in both Java 17 and Java 21 (supported LTE versions)

## Review Checklist
- [x] I have clicked on ["allow edits by
maintainers"](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/working-with-forks/allowing-changes-to-a-pull-request-branch-created-from-a-fork).
- [ ] I have added documentation for new/changed functionality in this
PR or in a PR to [openfga.dev](https://github.com/openfga/openfga.dev)
[Provide a link to any relevant PRs in the references section above]
- [x] The correct base branch is being used, if not `main`
- [ ] I have added tests to validate that the change in functionality is
working as expected

.github/workflows/checks.yaml

@@ -1,6 +1,10 @@
 name: Checks
 
-on: [pull_request, push]
+on:
+  merge_group:
+  push:
+  pull_request:
+  workflow_dispatch:
 
 jobs:
   fossa:
@@ -24,18 +28,24 @@ jobs:
         with:
           api-key: ${{ secrets.FOSSA_API_KEY }}
           run-tests: true
-  build:
+
+  test:
     name: Run Checks
     runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        java: [17, 21]
+
     steps:
       - name: Checkout the source
-        uses: actions/checkout@v4
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1
       - name: Validate Gradle wrapper
-        uses: gradle/wrapper-validation-action@v2
-      - name: Set up JDK 17
-        uses: actions/setup-java@v4
+        uses: gradle/wrapper-validation-action@b231772637bb498f11fdbc86052b6e8a8dc9fc92 # v2.1.2
+      - name: Set up JDK
+        uses: actions/setup-java@99b8673ff64fbf99d8d325f52d9a5bdedb8483e9 # v4.2.1
         with:
-          java-version: "17"
+          java-version: ${{ matrix.java }}
           distribution: "temurin"
       - name: Run Gradle check task
         run: ./gradlew check --continue