OpenAPI support for FromForm for MsgPack and TempFile

The package versions I am using:
```toml
rocket = { version = "0.5.0-rc.3", features = ["msgpack"] }
rocket_okapi = { version = "0.8.0-rc.3", features = ["swagger", "msgpack"] }
schemars = "0.8.15"
```

The form input structs and endpoint function I am using is as follows:
```rust
#[derive(FromForm)]
pub struct DataInput<'r> {
pub data_a: MsgPack,
pub data_b: TempFile<'r>,
}

#[derive(Debug, Serialize, Deserialize, JsonSchema)]
pub struct ResponseData {
pub values: Vec,
}

#[openapi(tag = "Data")]
#[post("/process_data", data = "")]
pub fn process_data(
data_input: Form>,
) -> Result, Status> { ... }
```

I am trying to work out if it is better to try implement `JsonSchema` or use `#[openapi(skip)]` and do a merge on a custom `OpenApi` struct with just this definition.

I was initially trying an `OpenApi` struct which is as follows.
```rust
pub fn process_data_openapi(schema_generator: &mut SchemaGenerator) -> OpenApi {
use indexmap::indexmap;
use rocket_okapi::okapi::openapi3::*;
OpenApi {
openapi: OpenApi::default_version(),
info: Default::default(),
servers: vec![],
paths: indexmap! {
"/process_data".to_owned() => PathItem {
post: Some(
Operation {
tags: vec!["Data".to_owned()],
summary: Some("Gets the data result from the given files.".to_owned()),
request_body: Some(RefOr::Object(
RequestBody {
description: Some("The data definition.".to_string()),
content: indexmap! {
"form-data".to_owned() => MediaType {
schema: Some(SchemaObject {
instance_type: Some(SingleOrVec::Vec(vec![
// TODO: Put definition here
])),
..Default::default()
}),
..Default::default()
}
},
..Default::default()
}
)),
responses: Responses {
responses: indexmap! {
"200".to_owned() => RefOr::Object(
Response {
description: "The response data".to_owned(),
content: indexmap! {
"application/json".to_owned() => MediaType {
schema: Some(ResponseData::json_schema(schema_generator).into()),
..Default::default()
}
},
..Default::default()
}
)
},
..Default::default()
},
..Default::default()
}
),
..Default::default()
},
},
..Default::default()
}
}
```

As you can see I'm not sure how to define the `MediaType` `SchemaObject` for the `form-data`

Are there any existing proc_macros that could help me or traits that I could implement?

Any help would be greatly appreciated.