Redesign the lookup of attribute of the Pipeline object

[stiebels]

Problem Statement
The general path parsing, attribute lookup and filter functionality is convoluted and requires re-design:

• Validation.get_attribute
• Validation.get_filtered_attribute

Target State
The overall objective is to make the implementation of new Validations as easy as possible by providing developers and users a robust and general functionality to search and filter for the desired attribute (value).

More concretely:

• Generalized lookup functionality that can be used across Validations to find appropriate attributes of any object.
• Should allow for filtering based on user input:
  • indices, e.g. if an attribute is a list and the user wants to fetch the first item of that attribute/list
  • value of attributes, e.g. if an attribute is a dict or other complex object