CI improvements (#4)

* Make deploy dependent on succesful testing
* Use cache action v4
* Test on ubuntu 24.04

.github/workflows/test_and_deploy.yml

@@ -3,7 +3,7 @@ on: push
 
 jobs:
   test:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
       - uses: erlef/setup-beam@v1
@@ -12,7 +12,7 @@ jobs:
           version-file: .tool-versions
       - name: Cache deps
         id: cache-deps
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-name: cache-elixir-deps
         with:
@@ -26,7 +26,7 @@ jobs:
       # project's downloaded deps every run.
       - name: Cache compiled build
         id: cache-build
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         env:
           cache-name: cache-compiled-build
         with:
@@ -53,6 +53,7 @@ jobs:
 
   deploy:
     name: Deploy app
+    needs: test
     runs-on: ubuntu-latest
     if: github.ref == 'refs/heads/main'
     concurrency: deploy-group    # optional: ensure only one action runs at a time