docker-compose.yml: fix yaml

Fix this error:

docker-compose --file docker-compose.yml config
parsing /Users/vlad/src/rss-email-subscription/docker-compose.yml: yaml: unmarshal errors:
  line 56: mapping key "<<" already defined at line 55
  line 84: mapping key "<<" already defined at line 83
  line 103: mapping key "<<" already defined at line 102
  line 118: mapping key "<<" already defined at line 117
  line 136: mapping key "<<" already defined at line 135
  line 154: mapping key "<<" already defined at line 153
  line 168: mapping key "<<" already defined at line 167

NOTE: This started after Docker update, which used a newer version of
YAML library. Please see docker/compose#10411.

docker-compose.yml

@@ -52,8 +52,7 @@ services:
       POSTFIX_fragile_destination_concurrency_limit: 1
       POSTFIX_fragile_destination_rate_delay: 2s
 
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
     healthcheck:
       disable: true # Disabled because makes it makes following the logs harder when degugging
 
@@ -80,8 +79,7 @@ services:
       # TLS: No ECDSA certificate in this setup, only RSA
       SMF_POSTFIXMAIN_smtpd_tls_eccert_file: ''
       SMF_POSTFIXMAIN_smtpd_tls_eckey_file: ''
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   app:
     depends_on: [logger]
@@ -99,8 +97,7 @@ services:
     environment:
       <<: *app-env
     command: node dist/app/cron.js
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   delmon:
     depends_on: [logger]
@@ -114,8 +111,7 @@ services:
       - ${DATA_DIR_ROOT?}:/data
     environment:
       <<: *app-env
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   api:
     depends_on: [logger]
@@ -132,8 +128,7 @@ services:
       # DEBUG: 'express:*'
       # TS_NODE_DEBUG: 'true'
       <<: *app-env
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   # Thanks to https://github.com/wmnnd/nginx-certbot
   website:
@@ -150,8 +145,7 @@ services:
       - ./.tmp/certbot/www:/var/www/certbot
     environment:
       NGINX_HOST: feedsubscription.com
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   # Thanks to https://github.com/wmnnd/nginx-certbot
   certbot:
@@ -164,8 +158,7 @@ services:
       - ./.tmp/certbot/conf:/etc/letsencrypt
       - ./website/html:/var/www/certbot
     entrypoint: "/bin/sh -c 'trap exit TERM; while :; do date; certbot renew; sleep 7d & wait $${!}; done;'"
-    <<: *logging
-    <<: *dns
+    <<: [*logging, *dns]
 
   logger:
     container_name: logger