Ensure INSTANCE_DOMAIN propagates to containers (#358)

.env.example

@@ -57,6 +57,11 @@ CONTACT_LINK='#potatomesh:dod.ngo'
 # Debug mode (0=off, 1=on)
 DEBUG=0
 
+# Public domain name for this PotatoMesh instance
+# Provide a hostname (with optional port) that resolves to the web service.
+# Example: mesh.example.org or mesh.example.org:41447
+INSTANCE_DOMAIN=mesh.example.org
+
 # Docker image architecture (linux-amd64, linux-arm64, linux-armv7)
 POTATOMESH_IMAGE_ARCH=linux-amd64