Fix cache for Docker buildx (#1750)

~~This is an attempt to fix the CI bug
[here](https://github.com/firezone/firezone/actions/runs/5491388141/jobs/10007864417#step:4:1638)
possibly introduced in
[d9eb2d18](https://github.com/firezone/firezone/commit/d9eb2d18#diff-88bd94db0d5cfd5f0617b7c4ed48c0212597378ed7e28714c5d86c95999b4c7dR29)
and uncovered / exacerbated in Elixir 1.15~~

Edit: looks like this ended up being a couple cache issues with GitHub
actions:
1. The `elixir_api-container-build` cache would always overwrite the
`elixir_web-container-build` on subsequent builds of the same
`github.ref_name` (cache is scoped to branch name by default), leading
to the consistent error `Elixir.Web.Mailer.NoopAdapter does not exist`
whenever a branch was pushed to more than once.
2. The same thing happens with the `integration_test-basic-flow` job
because the `api` service gets built after the `web` service in
docker-compose.yml, overwriting its cache

For some reason it seems the `APPLICATION_NAME` ARG is not busting the
Docker cache properly on GitHub actions for elixir container builds, so
the fix here was to [use
`scope=`](https://docs.docker.com/build/cache/backends/gha/#scope) to
segregate the cache layers between builds of the same branch.

.github/workflows/elixir.yml

@@ -458,8 +458,8 @@ jobs:
             APPLICATION_NAME=${{ env.APPLICATION_NAME }}
             APPLICATION_VERSION=0.0.0-sha.${{ github.sha }}
           context: elixir/
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          cache-from: type=gha,scope=${{ env.APPLICATION_NAME }}-${{ github.sha }}
+          cache-to: type=gha,mode=max,scope=${{ env.APPLICATION_NAME }}-${{ github.sha }}
           file: elixir/Dockerfile
           push: true
           tags: ${{ env.REGISTRY }}/${{ env.GCLOUD_PROJECT }}/firezone/${{ env.APPLICATION_NAME }}:${{ env.TAG }} , ${{ env.REGISTRY }}/${{ env.GCLOUD_PROJECT }}/firezone/${{ env.APPLICATION_NAME }}:${{ github.sha }}
@@ -518,8 +518,8 @@ jobs:
             APPLICATION_NAME=${{ env.APPLICATION_NAME }}
             APPLICATION_VERSION=0.0.0-sha.${{ github.sha }}
           context: elixir/
-          cache-from: type=gha
-          cache-to: type=gha,mode=max
+          cache-from: type=gha,scope=${{ env.APPLICATION_NAME }}-${{ github.sha }}
+          cache-to: type=gha,mode=max,scope=${{ env.APPLICATION_NAME }}-${{ github.sha }}
           file: elixir/Dockerfile
           push: true
           tags: ${{ env.REGISTRY }}/${{ env.GCLOUD_PROJECT }}/firezone/${{ env.APPLICATION_NAME }}:${{ env.TAG }} , ${{ env.REGISTRY }}/${{ env.GCLOUD_PROJECT }}/firezone/${{ env.APPLICATION_NAME }}:${{ github.sha }}

.github/workflows/integration-tests.yml

@@ -16,6 +16,13 @@ jobs:
       - name: Build images
         uses: docker/bake-action@v3
         with:
+          set: |
+            elixir.cache-from=scope=elixir,type=gha
+            elixir.cache-to=scope=elixir,type=gha,mode=max
+            api.cache-from=scope=api,type=gha
+            api.cache-to=scope=api,type=gha,mode=max
+            web.cache-from=scope=web,type=gha
+            web.cache-to=scope=web,type=gha,mode=max
           files: docker-compose.yml
           push: false
       - name: Seed database

elixir/Dockerfile

@@ -39,8 +39,7 @@ ARG APPLICATION_VERSION=0.0.0-dev.docker
 # Install pipeline and compile assets for Web app
 RUN cd apps/web \
     && mix assets.setup \
-    && mix assets.deploy \
-    && cd ../../
+    && mix assets.deploy
 
 # Compile the release
 RUN mix compile