chore: add mongo 4.2 upgrde script (openedx-unsupported#828)

upgrade_mongo_4_2.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -eu -o pipefail
+
+# This script will upgrade a devstack that was previosly running Mongo DB 4.0 to MongoDB 4.0
+
+. scripts/colors.sh
+
+# Upgrade to mongo 4.2
+export MONGO_VERSION=4.2.14
+
+echo
+echo -e "${GREEN}Restarting Mongo on version ${MONGO_VERSION}${NC}"
+make dev.up.mongo
+mongo_container="$(make --silent --no-print-directory dev.print-container.mongo)"
+
+echo -e "${GREEN}Waiting for MongoDB...${NC}"
+until docker exec "$mongo_container" mongo --eval 'db.serverStatus()' &> /dev/null
+do
+    printf "."
+    sleep 1
+done
+
+echo -e "${GREEN}MongoDB ready.${NC}"
+MONGO_VERSION_LIVE=$(docker exec -it "$mongo_container" mongo --quiet --eval "printjson(db.version())")
+MONGO_VERSION_COMPAT=$(docker exec -it "$mongo_container" mongo --quiet \
+    --eval "printjson(db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )['featureCompatibilityVersion'])")
+echo -e "${GREEN}Mongo Server version: ${MONGO_VERSION_LIVE}${NC}"
+echo -e "${GREEN}Mongo FeatureCompatibilityVersion version: ${MONGO_VERSION_COMPAT}${NC}"
+
+if echo "${MONGO_VERSION_COMPAT}" | grep -q "4\.0" ; then
+    echo -e "${GREEN}Upgrading FeatureCompatibilityVersion to 4.2${NC}"
+    docker exec -it "$mongo_container" mongo --eval "db.adminCommand( { setFeatureCompatibilityVersion: \"4.2\" } )"
+else
+    echo -e "${GREEN}FeatureCompatibilityVersion already set to 4.2${NC}"
+fi