Task Description (Required)

As part of our investigation into how to import model and model servers from multiple sources (e.g. Kubeflow, RHOAI MR, Quay, etc), we need to look at ways to import entities into the RHDH catalog, without relying upon a Git repository.

We have prototype some vanilla HTTP servers which, when their host names are added to Backstage's allowed hosts  configuration, but there are some minor hiccups because it is not a full on github server.

Backstage provides two non-git options for ingesting entities into the catalog:
1) Custom Entity Providers

2) Custom Processors

This issue will focus on the former (Custom Entity Providers)

Custom Entity Providers appear to be the recommended solution for ingesting catalog entities from external sources:

There are two main options for how to ingest data into the catalog: making a custom entity provider, or making a custom processor. They both have strengths and drawbacks, but the former would usually be preferred. Both options are presented in a dedicated subsection below.

But it also seems that there may be specific drawbacks to this approach, which we will need to consider within the scope of our problem (importing models/model servers into the catalog). Pre-existing plugins like the Keycloak plugin already make use of custom entity providers to import into the catalog, so this may be a good starting point.

Tasks:

1. Stand up a basic Backstage plugin in RHDH, from which a custom entity provider could be written
2. Investigate how Custom Entity Providers work, and how they might be used to import 
3. Document any drawbacks to this approach 
4. If possible, provide a basic proof of concept using catalog entity providers