Fastapi

* Fix handling an empty-body request with a required body param. PR [311](https://github.com/tiangolo/fastapi/pull/311).

* Fix broken link in docs: [Return a Response directly](https://fastapi.tiangolo.com/tutorial/response-directly/). PR [#306](https://github.com/tiangolo/fastapi/pull/306) by [dmontagu](https://github.com/dmontagu).

* Fix docs discrepancy in docs for [Response Model](https://fastapi.tiangolo.com/tutorial/response-model/). PR [#288](https://github.com/tiangolo/fastapi/pull/288) by [awiddersheim](https://github.com/awiddersheim).

* Add support for declaring a `Response` parameter:
* This allows declaring:
* [Response Cookies](https://fastapi.tiangolo.com/tutorial/response-cookies/).
* [Response Headers](https://fastapi.tiangolo.com/tutorial/response-headers/).
* An HTTP Status Code different than the default: [Response - Change Status Code](https://fastapi.tiangolo.com/tutorial/response-change-status-code/).
* All of this while still being able to return arbitrary objects (`dict`, DB model, etc).
* Update attribution to Hug, for inspiring the `response` parameter pattern.
* PR [294](https://github.com/tiangolo/fastapi/pull/294).

* Implement dependency cache per request.
* This avoids calling each dependency multiple times for the same request.
* This is useful while calling external services, performing costly computation, etc.
* This also means that if a dependency was declared as a *path operation decorator* dependency, possibly at the router level (with `.include_router()`) and then it is declared again in a specific *path operation*, the dependency will be called only once.
* The cache can be disabled per dependency declaration, using `use_cache=False` as in `Depends(your_dependency, use_cache=False)`.
* Updated docs at: [Using the same dependency multiple times](https://fastapi.tiangolo.com/tutorial/dependencies/sub-dependencies/#using-the-same-dependency-multiple-times).
* PR [292](https://github.com/tiangolo/fastapi/pull/292).

* Implement dependency overrides for testing.
* This allows using overrides/mocks of dependencies during tests.
* New docs: [Testing Dependencies with Overrides](https://fastapi.tiangolo.com/tutorial/testing-dependencies/).
* PR [291](https://github.com/tiangolo/fastapi/pull/291).

* Fix path and query parameters receiving `dict` as a valid type. It should be mapped to a body payload. PR [287](https://github.com/tiangolo/fastapi/pull/287). Updated docs at: [Query parameter list / multiple values with defaults: Using `list`](https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#using-list).

* Fix `auto_error=False` handling in `HTTPBearer` security scheme. Do not `raise` when there's an incorrect `Authorization` header if `auto_error=False`. PR [282](https://github.com/tiangolo/fastapi/pull/282).

* Fix type declaration of `HTTPException`. PR [279](https://github.com/tiangolo/fastapi/pull/279).

* Fix broken link in docs about OAuth 2.0 with scopes. PR [275](https://github.com/tiangolo/fastapi/pull/275) by [dmontagu](https://github.com/dmontagu).

* Refactor param extraction using Pydantic `Field`:
* Large refactor, improvement, and simplification of param extraction from *path operations*.
* Fix/add support for list *query parameters* with list defaults. New documentation: [Query parameter list / multiple values with defaults](https://fastapi.tiangolo.com/tutorial/query-params-str-validations/#query-parameter-list-multiple-values-with-defaults).
* Add support for enumerations in *path operation* parameters. New documentation: [Path Parameters: Predefined values](https://fastapi.tiangolo.com/tutorial/path-params/#predefined-values).
* Add support for type annotations using `Optional` as in `param: Optional[str] = None`. New documentation: [Optional type declarations](https://fastapi.tiangolo.com/tutorial/query-params/#optional-type-declarations).
* PR [278](https://github.com/tiangolo/fastapi/pull/278).