How do I adopt the PostgreSQL naming convention in legacy database?

I realize I'll need to update the queries, but if I have a database that has [camelCase](https://en.wikipedia.org/wiki/Camel_case) or spaces in it, you have to use double quotes on the identifiers (viz. schema, table, column). How do I migrate away from taking into account that I can't have capital letters, nor spaces in my identifiers. I need to normalize all of them to [snake_case](https://en.wikipedia.org/wiki/Snake_case) .