fix: expose connection identifier on connection objects

[DimitriKwihangana]

The fix is about adding a slug/identifier of a connection to the connection class in addition to the url and variables

Changes

• I Added identifier field to the Connection base class and pass it through when constructing all connection types, so the identifier used to fetch a connection is accessible on the returned object.
• Also fix IASOConnection to properly inherit from Connection.

How/what to test

• Run any pipeline that uses a connection parameter. After fetching the connection, print or log .identifier on it. it should return the slug used to fetch it.

[bramj]

Great @DimitriKwihangana ! This is really cool, I'm surprised it's such a small change.
Just a minor comment.

[bramj]

This is very clever! I think it could benefit from a documentation comment explaining what it does. (this seems to explain it well: https://stackoverflow.com/a/49911616)