Support for computed non-optional properties

[arjunrajshekhar]

Is your feature request related to a problem?

Assigning a property on a request/response model on the swagger spec as readOnly: true converts that property into an Optional: true and Computed: true property.

There doesn't appear to be any way to set a property with just Computed: true.

Example:

With the swaggercodegen example, run terraform providers schema -json

The computed input property for the swaggercodegen_cdn_v1 resource is marked as computed and optional

//.....
"computed": {
    "type": "string",
    "description_kind": "plain",
    "optional": true,
    "computed": true
  },
//.....

Describe the solution you'd like

It would be useful to have a method to mark a property as computed-only. Usually these would be readOnly properties from the swagger spec, but it looks like that's reserved for computed+optional properties, so perhaps an additional custom x-terraform-* field would be useful.

Acceptance criteria

The plugin has some means by which a non-optional computed property can be created on the output schema.

Additional context

The reason I have requested this is because I am looking to auto-generate terraform registry docs using the terraform-plugin-docs tool, and the fields that should be under the "Read Only" section appear under "Optional" instead, which doesn't really make sense for properties that are meant to only be read.

Semantically, a non-optional computed is the equivalent to a required readonly supported by OpenAPI v3, which is for properties you are guaranteed to see on a response.

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