## Description
As per [APG-113](https://hasurahq.atlassian.net/browse/APG-113), we
would like to remove the separate concept of supergraphs. This is the
first step: we allow the supergraph config to appear in subgraphs. The
next step will be to remove the non-subgraph version of it.
This PR updates the subgraph enum type to allow for supergraph config
objects, but does nothing else. This means it should be a no-op for
current users, but will be forward-compatible with the eventual goal of
the epic. We also throw in a makeshift test framework that we can
probably replace with Insta at a later date.
<!--
Questions to consider answering:
1. What user-facing changes are being made?
2. What are issues related to this PR? (Consider adding `(close
#<issue-no>)` to the PR title)
3. What is the conceptual design behind this PR?
4. How can this PR be tested/verified?
5. Does the PR have limitations?
6. Does the PR introduce breaking changes?
-->
## Changelog
- Add a changelog entry (in the "Changelog entry" section below) if the
changes
in this PR have any user-facing impact. See
[changelog
guide](https://github.com/hasura/graphql-engine-mono/wiki/Changelog-Guide).
- If no changelog is required ignore/remove this section and add a
`no-changelog-required` label to the PR.
### Product
_(Select all products this will be available in)_
- [x] community-edition
- [x] cloud
<!-- product : end : DO NOT REMOVE -->
### Type
<!-- See changelog structure:
https://github.com/hasura/graphql-engine-mono/wiki/Changelog-Guide#structure-of-our-changelog
-->
_(Select only one. In case of multiple, choose the most appropriate)_
- [ ] highlight
- [ ] enhancement
- [ ] bugfix
- [x] behaviour-change
- [ ] performance-enhancement
- [ ] security-fix
<!-- type : end : DO NOT REMOVE -->
### Changelog entry
<!--
- Add a user understandable changelog entry
- Include all details needed to understand the change. Try including
links to docs or issues if relevant
- For Highlights start with a H4 heading (#### <entry title>)
- Get the changelog entry reviewed by your team
-->
Supergraph configuration (`CompatibilityConfig`, `AuthConfig`, and
`GraphqlConfig`) may now be defined in any subgraph. Note that
supergraph configuration may still only be defined once for any given
supergraph.
<!-- changelog-entry : end : DO NOT REMOVE -->
<!-- changelog : end : DO NOT REMOVE -->
[APG-113]:
https://hasurahq.atlassian.net/browse/APG-113?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQ
V3_GIT_ORIGIN_REV_ID: a1b9911c4abb332fe37914efd1c3afbbd554a5d0
