Switchboard - a Go tool to query peers (MongoDB) (#3980)

Stacked on top of #3979 and #3978

Queries are Extended JSON, psql still treats those as strings and they
can be turned into BSON by mongo driver.
Has a help command that lists everything supported and links out to the
docs.

Author: ilidemi

flow/connectors/mongo/mongo.go

@@ -112,6 +112,10 @@ func NewMongoConnector(ctx context.Context, config *protos.MongoConfig) (*MongoC
 	return mc, nil
 }
 
+func (c *MongoConnector) Client() *mongo.Client {
+	return c.client
+}
+
 func (c *MongoConnector) Close() error {
 	var errs []error
 	if c != nil && c.client != nil {