Add ENV vars to config file, switch to ERB template

config.yml.erb.example

@@ -0,0 +1,17 @@
+development: &defaults
+  maintenance: false
+  redis:
+    host: <%= ENV["REDIS_HOST"] || "localhost" %>
+    port: <%= ENV["REDIS_PORT"] || "6379" %>
+  s3: &s3_defaults
+    endpoint: <%= ENV["S3_ENDPOINT"] || "http://127.0.0.1:9000" %>
+    region: <%= ENV["S3_REGION"] %>
+    access_key_id: <%= ENV["S3_ACCESS_KEY"] || "minioadmin" %>
+    secret_key_id: <%= ENV["S3_SECRET_KEY"] || "minioadmin" %>
+    bucket: <%= ENV["S3_BUCKET"] || "rs-development" %>
+test:
+  <<: *defaults
+staging:
+  <<: *defaults
+production:
+  <<: *defaults