new: [mongo] offer ``mongosh`` indirect action through ``mongo-database`` relation

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

mongo/actions/relations/mongo-database/mongosh

@@ -0,0 +1,96 @@
+#!/bin/bash
+## compose: no-hooks
+
+if [ -z "$SERVICE_DATASTORE" ]; then
+    echo "This script is meant to be run through 'compose' to work properly." >&2
+    exit 1
+fi
+
+version=0.1
+usage="$exname [-h|--help] DBNAME"
+help="
+USAGE:
+
+$usage
+
+DESCRIPTION:
+
+Read stdin and content to related $CHARM_NAME service in the database
+DBNAME. If DBNAME is not provided, it'll take the default database
+from the ${DARKCYAN}mongo-database${NORMAL} relation of current
+service.
+
+EXAMPLES:
+
+  $exname < foo.sql
+  $exname mydb2 < foo.sql
+
+"
+
+
+dbname=
+output=
+while [ "$1" ]; do
+    case "$1" in
+        "--help"|"-h")
+            print_help >&2
+            exit 0
+            ;;
+        "--force"|"-f")
+            force=yes
+            ;;
+        --*|-*)
+            err "Unexpected optional argument '$1'"
+            print_usage >&2
+            exit 1
+            ;;
+        *)
+            [ -z "$dbname" ] && { dbname=$1 ; shift ; continue ; }
+            err "Unexpected positional argument '$1'"
+            print_usage >&2
+            exit 1
+        ;;
+    esac
+    shift
+done
+
+
+if [ -z "$dbname" ]; then
+
+    ##
+    ## Fetch default dbname in relation to mongo-database
+    ##
+
+    ## XXXvlab: can't get real config here
+    if ! read-0 ts _ _ < <(get_service_relation "$SERVICE_NAME" "mongo-database"); then
+        err "Couldn't find relation ${DARKCYAN}mongo-database${NORMAL}."
+        exit 1
+    fi
+
+    relation_dir=$(get_relation_data_dir "$SERVICE_NAME" "$ts" "mongo-database") || {
+        err "Failed to find relation dir"
+        exit 1
+    }
+    mongo_config=$(cat "$relation_dir"/data) || exit 2
+
+    dbname="$(e "$mongo_config" | shyaml get-value dbname)" || {
+        err "Couldn't retrieve information of ${DARKCYAN}mongo-database${NORMAL}'s relation."
+        exit 1
+    }
+
+fi
+
+set -e
+
+containers="$(get_running_containers_for_service "$RELATION_TARGET_SERVICE")"
+
+if [ -z "$containers" ]; then
+    err "No containers running for service $DARKYELLOW$service$NORMAL."
+    exit 1
+fi
+
+
+## XXXvlab: taking first container is probably not a good idea
+container_id="$(echo "$containers" | head -n 1)"
+docker exec -i -u 0 \
+       "${container_id}" mongo --quiet "$dbname"