Make migration instructions more obvious

Author: thespad

Dockerfile

@@ -21,7 +21,7 @@ RUN \
     libcap2 \
     logrotate \
     openjdk-8-jre-headless && \
-  echo "**** download mongodb ****" && \
+  echo "**** install mongodb ****" && \
   curl -s https://www.mongodb.org/static/pgp/server-4.4.asc | apt-key add - && \
   echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/4.4 multiverse" | tee /etc/apt/sources.list.d/mongodb-org-4.4.list && \
   apt-get update && \

README.md

@@ -57,6 +57,10 @@ The architectures supported by this image are:
 
 Access the webui at `<your-ip>:8088`, for more information check out [omada-controller](https://www.tp-link.com/uk/support/download/omada-software-controller/).
 
+### Upgrades from v4 -> v5
+
+**Due to breaking changes it is necessary to take a backup of your v4 install, spin up a clean v5 container and then restore the backup.**
+
 ## Usage
 
 Here are some example snippets to help you get started creating a container.