fix(listmailuser): Don't parse comments when reading config (#2617)

* fix(listmailuser): Don't parse comments

Avoids passing comments to `dovecot_quota_to_hr()` which fails to handle it and would throws errors.

* chore: Move config filter method to `helpers/utils.sh`

target/bin/listmailuser

@@ -47,6 +47,7 @@ do
   else
     echo
   fi
-done < "${DATABASE}"
+done < <(_filter_to_valid_lines "${DATABASE}")
+
 
 exit 0

target/scripts/helpers/utils.sh

@@ -5,8 +5,16 @@ function _escape
   echo "${1//./\\.}"
 }
 
-# Check if string input is an empty line, only whitespaces
-# or `#` as the first non-whitespace character.
+# Returns input after filtering out lines that are:
+# empty, white-space, comments (`#` as the first non-whitespace character)
+function _filter_to_valid_lines
+{
+  grep --extended-regexp --invert-match "^\s*$|^\s*#" "${1}" || true
+}
+
+# TODO: Only used by `relay.sh`, will be removed in future.
+# Similar to _filter_to_valid_lines, but only returns a status code
+# to indicate invalid line(s):
 function _is_comment
 {
   grep -q -E "^\s*$|^\s*#" <<< "${1}"