new: [apache] custom rules support now sequences and struct to allow appending values.

apache/lib/common

@@ -458,9 +458,49 @@ EOF
 }
 
 
+_get_custom_rules() {
+    local custom_rules type elt value first
+    custom_rules=$(relation-get apache-custom-rules 2>/dev/null) || true
+    if [ -z "$custom_rules" ]; then
+        return 0
+    fi
+    type=$(echo "$custom_rules" | shyaml get-type)
+    value=
+    case "$type" in
+        "sequence")
+            first=1
+            while read-0 elt; do
+                elt="$(echo "$elt" | yaml_get_interpret)" || return 1
+                [ "$elt" ] || continue
+                if [ "$first" ]; then
+                    first=
+                else
+                    value+=$'\n'$'\n'
+                fi
+                first=
+                value+="$elt"
+            done < <(echo "$custom_rules" | shyaml -y get-values-0)
+            ;;
+        "struct")
+            while read-0 _key val; do
+                value+=$'\n'"$(echo "$val" | yaml_get_interpret)" || return 1
+            done < <(echo "$custom_rules" | shyaml -y key-values-0)
+            ;;
+        "str")
+            value+=$(echo "$custom_rules")
+            ;;
+        *)
+            value+=$(echo "$custom_rules")
+            ;;
+    esac
+    printf "%s" "$value"
+}
+
+
 __vhost_custom_rules() {
     local custom_rules
-    if custom_rules=$(relation-get apache-custom-rules 2>/dev/null); then
+    custom_rules=$(_get_custom_rules) || return 1
+    if [ "$custom_rules" ]; then
         cat <<EOF