Connect to a MySQL database
Usage
connect_mysql(
dbname = Sys.getenv("MYSQL_ADDON_DB"),
host = Sys.getenv("MYSQL_ADDON_HOST"),
port = Sys.getenv("MYSQL_ADDON_PORT"),
user = Sys.getenv("MYSQL_ADDON_USER"),
password = Sys.getenv("MYSQL_ADDON_PASSWORD")
)