Missing HTTP response codes in OpenAPI schema

[ml-evs]

While trying out the schemathesis library for fuzzy API testing based on schemas, I discovered that the response codes we provide in the OpenAPI schemas are limited.

I guess we need to somehow we make our exceptions handlers known to FastAPI? It seems like there is something a bit strange with our ErrorResponse being a valid "successful response", presumably because of the way we use our exception handlers. See e.g. for the links endpoint:

          "responses": {
            "200": {
              "description": "Successful Response",
              "content": {
                "application/json": {
                  "schema": {
                    "title": "Response Get Links Links Get",
                    "anyOf": [
                      {
                        "$ref": "#/components/schemas/LinksResponse"
                      },
                      {
                        "$ref": "#/components/schemas/ErrorResponse"
                      }
                    ]
                  }
                }
              }
            },
            "422": {
              "description": "Validation Error",
              "content": {
                "application/json": {
                  "schema": {
                    "$ref": "#/components/schemas/HTTPValidationError"
                  }
                }
              }
            }
          }
        }
      },

It would be nice to add e.g. 553 VersionNotSupported and other errors that are buried in the spec so that automated tools can use our API more effectively.

[CasperWA]

I think this is due to the response_model value we put for endpoint functions. We'd need to differentiate further in the same decorator.