Better handle of synapse SQL connection

- Do not fail if it is not configured
- Add missing configuration step

docs/features/experimental/application-service.md

@@ -19,8 +19,17 @@ matrix:
     localpart: 'appservice-mxisd'
     token:
       hs: 'HS_TOKEN_CHANGE_ME'
+
+synapseSql:
+  enabled: false ## Do not use this line if Synapse is used as an Identity Store
+  type: '<DB TYPE>'
+  connection: '<DB CONNECTION URL>'
 ```
 
+The `synapseSql` section is used to retrieve display names which are not directly accessible in this mode.
+For details about `type` and `connection`, see the [relevant documentation](../../stores/synapse.md).
+If you do not configure it, some placeholders will not be available in the notification, like the Room name.
+
 You can also change the default template of the notification using the `generic.matrixId` template option.  
 See [the Template generator documentation](../../threepids/notification/template-generator.md) for more info.
 

src/main/java/io/kamax/mxisd/as/AppServiceHandler.java

@@ -92,7 +92,12 @@ public void processTransaction(List<JsonObject> eventsJson) {
                     log.info("Found an email address to notify about room invitation: {}", tpid.getAddress());
                     Map<String, String> properties = new HashMap<>();
                     profiler.getDisplayName(sender).ifPresent(name -> properties.put("sender_display_name", name));
-                    synapse.getRoomName(roomId).ifPresent(name -> properties.put("room_name", name));
+                    try {
+                        synapse.getRoomName(roomId).ifPresent(name -> properties.put("room_name", name));
+                    } catch (RuntimeException e) {
+                        log.warn("Unable to fetch room name - Did you provide synapse DB information as documented?");
+                        log.warn("Underlying error:", e);
+                    }
 
                     IMatrixIdInvite inv = new MatrixIdInvite(roomId, sender, mxid, tpid.getMedium(), tpid.getAddress(), properties);
                     notif.sendForInvite(inv);