hardcode db_user rather than using a secret

.env.sample

@@ -7,6 +7,5 @@ DOMAIN=xwiki.example.com
 
 LETS_ENCRYPT_ENV=production
 
-SECRET_DB_USERNAME_VERSION=v1
 SECRET_DB_PASSWORD_VERSION=v1
 SECRET_DB_ROOT_PASSWORD_VERSION=v1

compose.yml

@@ -4,14 +4,13 @@ services:
   app:
     image: "xwiki:stable-mysql-tomcat"
     environment:
-      - DB_USER_FILE=/run/secrets/db_username
+      - DB_USER=xwiki
       - DB_PASSWORD_FILE=/run/secrets/db_password
       - DB_DATABASE=xwiki
       - DB_HOST=${STACK_NAME}_db
     volumes:
       - xwiki-data:/usr/local/xwiki
     secrets:
-      - db_username
       - db_password
     networks:
       - proxy
@@ -44,7 +43,7 @@ services:
       - mysql-data:/var/lib/mysql
     environment:
       - MYSQL_ROOT_PASSWORD_FILE=/run/secrets/db_root_password
-      - MYSQL_USER_FILE=/run/secrets/db_username
+      - MYSQL_USER=xwiki
       - MYSQL_PASSWORD_FILE=/run/secrets/db_password
       - MYSQL_DATABASE=xwiki
     command:
@@ -52,7 +51,6 @@ services:
       - "--collation-server=utf8mb4_bin"
       - "--explicit-defaults-for-timestamp=1"
     secrets:
-      - db_username
       - db_password
       - db_root_password
 
@@ -66,9 +64,6 @@ volumes:
   xwiki-data:
 
 secrets:
-  db_username:
-    name: ${STACK_NAME}_db_username_${SECRET_DB_USERNAME_VERSION}
-    external: true
   db_password:
     name: ${STACK_NAME}_db_password_${SECRET_DB_PASSWORD_VERSION}
     external: true