Move custom implementations for enhanced functionality into this module

Problem/Motivation

We extended this module a lot by a custom module. Parts of that might be very interesting for this module. but it will be a bunch of work to refactor it. If anyone is interested to sponsor that for his own needs, we can do it.

Functionality for example includes:

• Custom Drupal signup & upgrade forms
• Entities for Components, Plans and Plan Variants
• Blocks and views for feature comparison
• Helper methods for typical needs
• ...

Steps to reproduce

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes