Feature Request

What

1. Remove @internal on methods in Doctrine\DBAL\Connection that could be reused in wrapper_class
2. Add the possibility to increment the transactionNestingLevel in a class that extends Doctrine\DBAL\Connection

Why

I'm developping a custom Doctrine\DBAL\Connection (for handling my own custom transaction management) and used the wrapper_class configuration parameter to setup my custom connection.

To do so, I extended the original Doctrine\DBAL\Connection and saw that:

1. Some methods have the @internal annotation:
   a. convertException
   b. getParams
2. The transactionNestingLevel property does not have the protected visibility and has no setter.

How

1. Remove the @internal annotation on convertException and getParams
2. Create a setter for transactionNestingLevel or change the property visibility to protected