Aid adoption of openedx-filters

[kdmccormick]

Background

Adoption of robust plugin systems, notably openedx-filters and openedx-events, is critical for both:

• the long-term maintainability of edx-platform, and
• the businesses which rely on Open edX as a platform for their solutions.

2U has recently begun trying out openedx-filters as a way to address their business needs without coupling their business logic with edx-platform. For context, see the discussion on this PR.

To do

2U engineers have highlighted some challenges they see in adopting openedx-filters. We want to unblock them in the short-term, while also paving the way for other teams to build using openedx-filters in the near future. Let's collect the problems and delegate here.

Immediate needs / reviews

Beta Give feedback

1. feat: Added a filter for modifying the course home url for externally hosted courses #90
   +0
   
2. feat: Added filter for modifying course home url for externally hosted courses edx-platform#32294
   +0
   

Next steps

Beta Give feedback

1. Document OPEN_EDX_FILTERS_CONFIG in edx-platform common settings
2. Link to hooks docs from openedx-filters and openedx-events READMEs
3. More docs for using openedx-filters in practice
4. Design discussion: Are filters appropriate for single function replacement?
5. Education: Add links to relevant videos
6. Education: Host Hooks workshop?
7. Explanation of Hooks Plugins vs. old-style plugins