exp(drone): figuring out anchors and multiple pipelines

.drone.yml

@@ -86,7 +86,7 @@ trigger:
 
 steps:
   - name: restore cache
-    image: *drone_cache
+    image: &drone_cache 'meltwater/drone-cache:v1.4.0'
     environment:
       AWS_ACCESS_KEY_ID:
         from_secret: minio_user
@@ -105,7 +105,7 @@ steps:
       restore: true
 
   - name: compile app
-    image: *elixir
+    image: &elixir 'elixir:1.15.7-slim'
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix compile --all-warnings --warnings-as-errors