Allow users to perform dry-runs on resources (with optional validation with a schema)

[imsdu]

Motivation
Delta does not provide any endpoint that would allow users to perform dry-runs on resources when this can be useful to test and debug without performing any writes to the primary store.

As the lower layers of Delta already allow to perform dry-runs, we want to make this available with a new endpoint which would allow users to test resources with and without a schema validation

Acceptance criteria

1. When a user calls this endpoint, no write operation to the primary store is done
2. The user must provide a valid resource payload following the same rules as the create and update operations of a resource
3. Optionally the user can also provide a schema to validate this resource with:

• A reference to an existing schema (with an optional revision/tag)
• The payload of a new schema

4. When the resource is valid, then it is returned to the user (the same as the result of the fetch operation)
5. When the resource can't be validated with the provided schema then an error containing the resulting resource and the validation report is returned to the user
6. When the resource is not valid for any other reason (the resource payload is invalid, the provided schema reference does not exist), an appropriate message is returned to the user

API changes
An example of requests would be:
With no validation

POST /v1/dry-run/resources/{org}/{project}
 {
   "resource": {
    "@context": [
      "https://bbp.neuroshapes.org"
    ],
    "@id": "https://bbp.epfl.ch/nexus/v1/realms/bbp/users/bob",
    "@type": [
      "Person",
      "Agent"
    ],
    "email": "[email protected]",
    "familyName": "Doe",
    "givenName": "Bob",
  }
}

With validation with a new schema

POST /v1/dry-run/resources/{org}/{project}
  "schema": {
    "@type": "ExistingSchema",
    "@id": "nxv:mySchema"
  },
  "resource": {
    "@context": [
      "https://bbp.neuroshapes.org"
    ],
    "@id": "https://bbp.epfl.ch/nexus/v1/realms/bbp/users/bob",
    "@type": [
      "Person",
      "Agent"
    ],
    "email": "[email protected]",
    "familyName": "Doe",
    "givenName": "Bob",
  }
}

With validation with a new schema

POST /v1/dry-run/resources/{org}/{project}
  "schema": {
    "@type": "NewSchema",
    "value": { ... } # SHACL schema
  },
  "resource": {
    "@context": [
      "https://bbp.neuroshapes.org"
    ],
    "@id": "https://bbp.epfl.ch/nexus/v1/realms/bbp/users/bob",
    "@type": [
      "Person",
      "Agent"
    ],
    "email": "[email protected]",
    "familyName": "Doe",
    "givenName": "Bob",
  }
}

[crisely09]

For the first case, does it need to be of @type: Unconstrained or is it just a placeholder for any type?

[imsdu]

@crisely09 It can be something else, it is just that whenever something is not validated today, its schema is https://bluebrain.github.io/nexus/schemas/unconstrained.json so I wanted to reuse the same vocabulary