Escape unicode in server.properties by default when less than 1.20 (#2480)

docs/configuration/server-properties.md

@@ -26,7 +26,7 @@ renders
 
 !!! note "Escape unicode"
 
-    Some Minecraft versions and server types do not support unicode characters, such as §, in `server.properties`. In those cases, an extra "\u00C2" will appear in the file and the client will render those as  characters. Unicode characters can be written as escaped codes by setting the environment variable `SERVER_PROPERTIES_ESCAPE_UNICODE` to "true".
+    For Minecraft versions less than 1.20, unicode characters in `server.properties` will be escaped as `\uXXXX`, by default. That behavior can be altered by setting `SERVER_PROPERTIES_ESCAPE_UNICODE` to "true" or "false".
 
 To produce a multi-line MOTD, embed a newline character as `\n` in the string, such as
 

scripts/start-setupServerProperties

@@ -25,6 +25,7 @@ function customizeServerProps {
   # normalize MOTD
   if [[ ${TYPE^^} = LIMBO ]]; then
     if [[ $MOTD ]] && ! [[ $MOTD =~ ^{ ]]; then
+      # shellcheck disable=SC2089
       MOTD="{\"text\":\"${MOTD}\"}"
     fi
   fi
@@ -110,11 +111,17 @@ function customizeServerProps {
 
   setPropertiesArgs=(
     --definitions "/image/property-definitions.json"
-    --escape-unicode="${SERVER_PROPERTIES_ESCAPE_UNICODE:-false}"
   )
   if [[ -v CUSTOM_SERVER_PROPERTIES ]]; then
     setPropertiesArgs+=(--custom-properties "$CUSTOM_SERVER_PROPERTIES")
   fi
+  if [[ -v SERVER_PROPERTIES_ESCAPE_UNICODE ]]; then
+    if isTrue "$SERVER_PROPERTIES_ESCAPE_UNICODE"; then
+      setPropertiesArgs+=(--escape-unicode)
+    fi
+  elif versionLessThan '1.20'; then
+    setPropertiesArgs+=(--escape-unicode)
+  fi
 
   handleDebugMode
   if ! mc-image-helper set-properties "${setPropertiesArgs[@]}" "$SERVER_PROPERTIES"; then