net/haproxy: only accept a single value for backend/server fields, refs #2266

When Multiple=Y is set, then backend/server fields are preselected.
This makes it impossible to remove backends/servers, even when the rule
does not actually use them.

net/haproxy/pkg-descr

@@ -6,6 +6,11 @@ very high loads while needing persistence or Layer7 processing.
 Plugin Changelog
 ================
 
+3.1
+
+Changed:
+* rules: only accept a single value for backend/server fields (#2266)
+
 3.0
 
 Added:

net/haproxy/src/opnsense/mvc/app/models/OPNsense/HAProxy/HAProxy.xml

@@ -2086,7 +2086,7 @@
                         </template>
                     </Model>
                     <ValidationMessage>Related backend item not found</ValidationMessage>
-                    <Multiple>Y</Multiple>
+                    <Multiple>N</Multiple>
                     <Required>N</Required>
                 </use_backend>
                 <use_server type="ModelRelationField">
@@ -2098,7 +2098,7 @@
                         </template>
                     </Model>
                     <ValidationMessage>Related server item not found</ValidationMessage>
-                    <Multiple>Y</Multiple>
+                    <Multiple>N</Multiple>
                     <Required>N</Required>
                 </use_server>
                 <http_request_auth type="TextField">