set default false env vars to blank instead of string literal 'false'

app/Dockerfile

@@ -35,8 +35,8 @@ ENV DB_PORT="5432"
 # config.php defaults
 ENV MYSQL_CHARSET="UTF8"
 ENV SELF_URL_PATH="%SELF_URL_PATH"
-ENV SINGLE_USER_MODE="false"
+ENV SINGLE_USER_MODE=""
-ENV SIMPLE_UPDATE_MODE="false"
+ENV SIMPLE_UPDATE_MODE=""
 ENV PHP_EXECUTABLE="/usr/bin/php"
 ENV LOCK_DIRECTORY="lock"
 ENV CACHE_DIR="cache"
@@ -45,7 +45,7 @@ ENV ICONS_URL="feed-icons"
 ENV AUTH_AUTO_CREATE="true"
 ENV AUTH_AUTO_LOGIN="true"
 ENV FORCE_ARTICLE_PURGE="0"
-ENV ENABLE_REGISTRATION="false"
+ENV ENABLE_REGISTRATION=""
 ENV REG_NOTIFY_ADDRESS="user@your.domain.dom"
 ENV REG_MAX_USERS="10"
 ENV SESSION_COOKIE_LIFETIME="86400"
@@ -53,7 +53,7 @@ ENV SMTP_FROM_NAME="Tiny Tiny RSS"
 ENV SMTP_FROM_ADDRESS="noreply@your.domain.dom"
 ENV DIGEST_SUBJECT="[tt-rss] New headlines for last 24 hours"
 ENV CHECK_FOR_UPDATES="true"
-ENV ENABLE_GZIP_OUTPUT="false"
+ENV ENABLE_GZIP_OUTPUT=""
 ENV PLUGINS="auth_internal, note"
 ENV LOG_DESTINATION="sql"
 ENV CONFIG_VERSION="26"

docker-compose.yml

@@ -1,8 +1,5 @@
 version: '3'
 
-# set database password in .env
-# please don't use quote (') or (") symbols in variables
-
 services:
   db:
     image: postgres:12-alpine