Non-Nexus Resource Creation Form in Fusion

**Motivation**

Today, users are limited to a JSON form when they want to create a new resource.
It would be good to move Nexus-specific resources' creation to the settings (e.g. views, resolvers), and have a place for users to create new resources of a non-Nexus type. This paves the way for editing a resource's metadata through a plugin: the user creates a new "empty" resource of a certain type, and it opens the resource view with a metadata edition plugin for that type.

Challenges:

- How do we define context?
- Should we have autocomplete on type selection?
- How do we list available types?
- Could we read one or more ontologies or a Nexus project with types definition to power the creation?

**Acceptance criteria**

TODO

**Mockups**

TODO

**Not in scope**

TODO

No files, tests, or entry points are named. First clarify the Fusion settings and resource-creation entry points, define the supported context and type-listing behavior with maintainers, and establish acceptance criteria and mockups before implementation.

Written by the indexing model from the issue text.