Doctests not displayed correctly and #[doc = "string"] not visible in swagger UI

[DragonDev1906]

Expected Behavior

Everything in the docstring to be visible in the resulting openapi document, similar to how it is shown in cargo doc.

This unfortunately makes it hard to use doctests or include a string literal used in another test in the generated docs to ensure they're kept up-to-date. Which in my opinion would be a big benefit of putting the api specification in the rust code in the first place.

Note that so far I was not able to get code_sample(lang = "rust", source = "examples::JSON_WITNESS") to show up in the generated swagger UI either, which was my first attempt at adding additional information that is also checked with cargo test.

Actual Behavior

Code	openapi	cargo doc	rust_analyzer
/// Something	Yes	Yes	Yes
#[doc = "Test 123"]	No Yes	Yes	Yes
#[doc = include_str!("../../README.md")]	No	Yes	No
Doctests	As written, not hiding lines starting with #	Yes	Yes

In cargo doc

I've had to use a separate struct because the openapi type wasn't added to cargo doc due to being private.

In the swagger UI

Steps to Reproduce the Problem

1. Use the OpenApi macro, add a method to it and add the following docstring:

    /// Retrieve previously stored key material
    ///
    /// This also returns the access control list
    ///
    /// ### Example value (before encryption and base64 encoding)
    #[doc = include_str!("../../README.md")]
    #[doc = "Test 123"]
    ///
    /// ### Attempt 2
    /// ```
    /// println!("Hello");
    /// # todo!();
    /// println!("World")
    /// ```
    #[oai(
        path = "/session/:session_id/keys/:id",
        method = "get",
        tag = Tags::KeyManagement
    )]
    async fn get_key(
    // ...

3. Run cargo doc to see the results it generates
4. Run a binary with this API and the swagger UI enabled
5. Have a look at the description in the swagger UI (see screenshots)

Specifications

• Version: 4.0.0
• Platform: Linux
• Subsystem: poem-openapi