Add Docker to the CI

Author: AndreuCodina

.github/workflows/pull_request.yaml

@@ -47,12 +47,11 @@ jobs:
       #   shell: bash
 
       - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v3
+        uses: docker/setup-buildx-action@e468171a9de216ec08956ac3ada2f0791b6bd435 # v3.11.1
 
-      - name: Build and push
-        uses: docker/build-push-action@v6
+      - name: Build and push api
+        uses: docker/build-push-action@263435318d21b8e681c14492fe198d362a7d2c83 # v6.18.0c
         with:
-          context: .
           file: api/src/api/Dockerfile
           push: false