Fix custom domain removal from az containerapp up (#116)

* Fix microsoft/azure-container-apps#234

* Added history note.

Co-authored-by: Haroon Feisal <haroonfeisal@microsoft.com>
Co-authored-by: Haroon Feisal <38823870+haroonf@users.noreply.github.com>

src/containerapp/HISTORY.rst

@@ -8,9 +8,9 @@ Release History
 * Added parameter --environment to 'az containerapp list'
 * Added 'az containerapp revision label swap' to swap traffic labels
 * BREAKING CHANGE: 'az containerapp revision list' now shows only active revisions by default, added flag --all to show all revisions
+* Fixed but with 'az containerapp up' where custom domains would be removed when updating existing containerapp
 * Fixed bug with 'az containerapp auth update' when using --unauthenticated-client-action
 
-
 0.3.5
 ++++++
 * Add parameter --zone-redundant to 'az containerapp env create'

src/containerapp/azext_containerapp/custom.py

@@ -2344,7 +2344,10 @@ def containerapp_up_logic(cmd, resource_group_name, name, managed_env, image, en
 
     ingress_def = None
     if target_port is not None and ingress is not None:
-        ingress_def = IngressModel
+        if ca_exists:
+            ingress_def = containerapp_def["properties"]["configuration"]["ingress"]
+        else:
+            ingress_def = IngressModel
         ingress_def["external"] = external_ingress
         ingress_def["targetPort"] = target_port
         containerapp_def["properties"]["configuration"]["ingress"] = ingress_def