impl JsonSchema for serde_json::Value

[ralpha]

The current implementation for impl JsonSchema for Value where Value is serde_json::Value does not work well.
https://github.com/GREsau/schemars/blob/master/schemars/src/json_schema_impls/serdejson.rs

Because this is a very special type it might be tricky.
Currently when this value is included in a response it will not set a type.
When a description is given it will set that. But that is about it.
The 'value' variable is the serde_json::Value type in the screenshot below.

Because of this UI's have a hard time parsing this.
RapiDoc: (an okay response)

Swagger UI: (Does not even acknowledge it, but in schema it is better)

I know these are issues with UI's and not Schemars. And the Spec does not really give any option for this.
But maybe we can use "allOf", "oneOf", "anyOf" to allow all types ("integer", "number", "string" and "boolean"). This will make sure there is at least something good there.

[GREsau]

Schemars is doing the right thing here, as "type" is not a required property in JSON Schema or OpenAPI 3 Schema objects (as confirmed in OAI/OpenAPI-Specification#1657).

Swagger UI seems to handle this ok in my opinion - the property doesn't appear in the example, but this would be fixed by GREsau/okapi#11. And to be honest I don't think it's much better when we include all types in "anyOf":

I don't think these slightly odd behaviours in third-party UIs are enough to warrant adding workarounds in Schemars.

If you do want to include all types in an "anyOf" for any schemas without a "type", you can do this in your application by writing a Visitor (which I still need to document 😅) that applies this change to any typeless schemas