OpenAPI.Server - the basePath not work as intended

[ndy2]

Hi. I found an issue related to OpenAPI.Server specification.
the Server in OpenAPI 3.0 combines host and basePath from OpenAPI 2.0 and the basePath part not work as intended.

---

In sample pet store case,

the /pet path should route to /api/v3/pet.

But, if we use SwaggerRouteDSL.getWithDoc, it whould register actual endpoint /pet instead of /api/v3/pet

def getWithDoc[RequestType: Manifest, ResponseType: Manifest](route: String,
                                                                name: String = "",
                                                                admin: Boolean = false,
                                                                routeIndex: Option[RouteIndex] = None,
                                                                registerOptionsRequest: Boolean = false)
                                                               (doc: Operation => Operation)
                                                               (callback: RequestType => ResponseType): Unit = {
    registerOperation(route, HttpMethod.GET)(doc)
    get(prependBasePath(route), name, admin, routeIndex)(callback)
    if (registerOptionsRequest) {
      options(route, name, admin, routeIndex)(noopCallback)
    }
  }

def prependBasePath(route) String {
   ???
}

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First, I think we could get basePath from the OpenAPI.servers property but it is not applicable for some use case where it has
multiple server object with different basePath.

If the SwaggerController supply some overidable configuration for the basePath with default of empty string, and it may be used at the prependBasePath above or some.

---

If I go on some PR for this, I would leave a comment.