Github actions use nix

.github/workflows/ci.yml

@@ -5,32 +5,18 @@ on:
       - master
 jobs:
   ci-matrix:
-    runs-on: ubuntu-22.04
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
-      matrix:
-        java: [ 'openjdk@1.17' ]
     steps:
       - uses: actions/checkout@v4.1.1
         with:
           fetch-depth: 100
-      - uses: jorelali/setup-elm@v5
-        with:
-          elm-version: 0.19.1
-      - uses: bahmutov/npm-install@v1
-        with:
-          working-directory: modules/webapp
       - name: Fetch tags
         run: git fetch --depth=100 origin +refs/tags/*:refs/tags/*
-      - uses: olafurpg/setup-scala@v14
-        with:
-          java-version: ${{ matrix.java }}
-      # - name: Coursier cache
-      #   uses: coursier/cache-action@v6
+      - uses: cachix/install-nix-action@v26
       - name: sbt ci ${{ github.ref }}
-        run: sbt ci
-        env:
-          SBT_OPTS: "-Xmx2G -Xss4m"
+        run: nix develop .#ci --command sbt ci
   ci:
     runs-on: ubuntu-22.04
     needs: [ci-matrix]