exp(drone): use yaml aliases for images

.drone.yml

@@ -9,7 +9,7 @@ trigger:
 
 steps:
   - name: database healthcheck
-    image: 'postgres:16.0-alpine'
+    image: &postgres 'postgres:16.0-alpine'
     environment:
       PGUSER: postgres
       PGPASSWORD: postgres
@@ -18,7 +18,7 @@ steps:
       - while ! pg_isready; do sleep 1; done
 
   - name: restore cache
-    image: 'meltwater/drone-cache:v1.4.0'
+    image: &drone_cache 'meltwater/drone-cache:v1.4.0'
     environment:
       AWS_ACCESS_KEY_ID:
         from_secret: minio_user
@@ -37,7 +37,7 @@ steps:
       restore: true
 
   - name: test
-    image: 'elixir:1.15.7-slim'
+    image: &elixir 'elixir:1.15.7-slim'
     environment:
       MIX_ENV: test
       POSTGRES_HOST: db
@@ -49,7 +49,7 @@ steps:
       - mix test --cover --trace --slowest 10
 
   - name: rebuild cache
-    image: 'meltwater/drone-cache:v1.4.0'
+    image: *drone_cache
     environment:
       AWS_ACCESS_KEY_ID:
         from_secret: minio_user
@@ -70,7 +70,7 @@ steps:
 
 services:
   - name: db
-    image: 'postgres:16.0-alpine'
+    image: *postgres
     environment:
       POSTGRES_USER: postgres
       POSTGRES_PASSWORD: postgres
@@ -86,7 +86,7 @@ trigger:
 
 steps:
   - name: restore cache
-    image: 'meltwater/drone-cache:v1.4.0'
+    image: *drone_cache
     environment:
       AWS_ACCESS_KEY_ID:
         from_secret: minio_user
@@ -105,13 +105,13 @@ steps:
       restore: true
 
   - name: compile app
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix compile --all-warnings --warnings-as-errors
 
   - name: audit deps
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - apt-get update
       - apt-get install -y git
@@ -122,31 +122,31 @@ steps:
       # - mix hex.outdated
 
   - name: format check
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix format --dry-run --check-formatted
 
   - name: credo check
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix credo suggest --strict --format=flycheck
 
   - name: dialyzer check
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix dialyzer --no-check --quiet --ignore-exit-status --format short
 
   - name: sobelow check
-    image: 'elixir:1.15.7-slim'
+    image: *elixir
     commands:
       - mix do local.rebar --force, local.hex --force, deps.get, deps.compile
       - mix sobelow
 
   - name: rebuild cache
-    image: 'meltwater/drone-cache:v1.4.0'
+    image: *drone_cache
     environment:
       AWS_ACCESS_KEY_ID:
         from_secret: minio_user