Fastapi

* Add GitHub social preview images to git. PR [752](https://github.com/tiangolo/fastapi/pull/752).
* Update PyPI "trove classifiers". PR [751](https://github.com/tiangolo/fastapi/pull/751).
* Add full support for Python 3.8. Enable Python 3.8 in full in Travis. PR [749](https://github.com/tiangolo/fastapi/pull/749).
* Update "new issue" templates. PR [749](https://github.com/tiangolo/fastapi/pull/749).
* Fix serialization of errors for exotic Pydantic types. PR [748](https://github.com/tiangolo/fastapi/pull/748) by [dmontagu](https://github.com/dmontagu).

* Add GitHub action [Issue Manager](https://github.com/tiangolo/issue-manager). PR [#742](https://github.com/tiangolo/fastapi/pull/742).
* Fix typos in docs. PR [734](https://github.com/tiangolo/fastapi/pull/734) by [bundabrg](https://github.com/bundabrg).
* Fix usage of `custom_encoder` in `jsonable_encoder`. PR [715](https://github.com/tiangolo/fastapi/pull/715) by [matrixise](https://github.com/matrixise).
* Fix invalid XML example. PR [710](https://github.com/tiangolo/fastapi/pull/710) by [OcasoProtal](https://github.com/OcasoProtal).
* Fix typos and update wording in deployment docs. PR [700](https://github.com/tiangolo/fastapi/pull/700) by [marier-nico](https://github.com/tiangolo/fastapi/pull/700).
* Add note about dependencies in `APIRouter` docs. PR [698](https://github.com/tiangolo/fastapi/pull/698) by [marier-nico](https://github.com/marier-nico).
* Add support for async class methods as dependencies [681](https://github.com/tiangolo/fastapi/pull/681) by [frankie567](https://github.com/frankie567).
* Add FastAPI with Swagger UI cheatsheet to external links. PR [671](https://github.com/tiangolo/fastapi/pull/671) by [euri10](https://github.com/euri10).
* Fix typo in HTTP protocol in CORS example. PR [647](https://github.com/tiangolo/fastapi/pull/647) by [forestmonster](https://github.com/forestmonster).
* Add support for Pydantic versions `1.0.0` and above, with temporary (deprecated) backwards compatibility for Pydantic `0.32.2`. PR [646](https://github.com/tiangolo/fastapi/pull/646) by [dmontagu](https://github.com/dmontagu).

* Update docs to reduce gender bias. PR [645](https://github.com/tiangolo/fastapi/pull/645) by [ticosax](https://github.com/ticosax).
* Add docs about [overriding the `operationId` for all the *path operations*](https://fastapi.tiangolo.com/tutorial/path-operation-advanced-configuration/#using-the-path-operation-function-name-as-the-operationid) based on their function name. PR [642](https://github.com/tiangolo/fastapi/pull/642) by [SKalt](https://github.com/SKalt).
* Fix validators in models generating an incorrect key order. PR [637](https://github.com/tiangolo/fastapi/pull/637) by [jaddison](https://github.com/jaddison).
* Generate correct OpenAPI docs for responses with no content. PR [621](https://github.com/tiangolo/fastapi/pull/621) by [brotskydotcom](https://github.com/brotskydotcom).
* Remove `$` from Bash code blocks in docs for consistency. PR [613](https://github.com/tiangolo/fastapi/pull/613) by [nstapelbroek](https://github.com/nstapelbroek).
* Add docs for [self-serving docs' (Swagger UI) static assets](https://fastapi.tiangolo.com/tutorial/extending-openapi/#self-hosting-javascript-and-css-for-docs), e.g. to use the docs offline, or without Internet. Initial PR [557](https://github.com/tiangolo/fastapi/pull/557) by [svalouch](https://github.com/svalouch).
* Fix `black` linting after upgrade. PR [682](https://github.com/tiangolo/fastapi/pull/682) by [frankie567](https://github.com/frankie567).

* Add dependencies with `yield`, a.k.a. exit steps, context managers, cleanup, teardown, ...
* This allows adding extra code after a dependency is done. It can be used, for example, to close database connections.
* Dependencies with `yield` can be normal or `async`, **FastAPI** will run normal dependencies in a threadpool.
* They can be combined with normal dependencies.
* It's possible to have arbitrary trees/levels of dependencies with `yield` and exit steps are handled in the correct order automatically.
* It works by default in Python 3.7 or above. For Python 3.6, it requires the extra backport dependencies:
* `async-exit-stack`
* `async-generator`
* New docs at [Dependencies with `yield`](https://fastapi.tiangolo.com/tutorial/dependencies/dependencies-with-yield/).
* Updated database docs [SQL (Relational) Databases: Main **FastAPI** app](https://fastapi.tiangolo.com/tutorial/sql-databases/#main-fastapi-app).
* PR [595](https://github.com/tiangolo/fastapi/pull/595).
* Fix `sitemap.xml` in website. PR [598](https://github.com/tiangolo/fastapi/pull/598) by [samuelcolvin](https://github.com/samuelcolvin).

* Upgrade required Starlette to `0.12.9`, the new range is `>=0.12.9,<=0.12.9`.
* Add `State` to FastAPI apps at `app.state`.
* PR [593](https://github.com/tiangolo/fastapi/pull/593).
* Improve handling of custom classes for `Request`s and `APIRoute`s.
* This helps to more easily solve use cases like:
* Reading a body before and/or after a request (equivalent to a middleware).
* Run middleware-like code only for a subset of *path operations*.
* Process a request before passing it to a *path operation function*. E.g. decompressing, deserializing, etc.
* Processing a response after being generated by *path operation functions* but before returning it. E.g. adding custom headers, logging, adding extra metadata.
* New docs section: [Custom Request and APIRoute class](https://fastapi.tiangolo.com/tutorial/custom-request-and-route/).
* PR [589](https://github.com/tiangolo/fastapi/pull/589) by [dmontagu](https://github.com/dmontagu).
* Fix preserving custom route class in routers when including other sub-routers. PR [538](https://github.com/tiangolo/fastapi/pull/538) by [dmontagu](https://github.com/dmontagu).

* Add notes to docs about installing `python-multipart` when using forms. PR [574](https://github.com/tiangolo/fastapi/pull/574) by [sliptonic](https://github.com/sliptonic).
* Generate OpenAPI schemas in alphabetical order. PR [554](https://github.com/tiangolo/fastapi/pull/554) by [dmontagu](https://github.com/dmontagu).
* Add support for truncating docstrings from *path operation functions*.
* New docs at [Advanced description from docstring](https://fastapi.tiangolo.com/tutorial/path-operation-advanced-configuration/#advanced-description-from-docstring).
* PR [556](https://github.com/tiangolo/fastapi/pull/556) by [svalouch](https://github.com/svalouch).
* Fix `DOCTYPE` in HTML files generated for Swagger UI and ReDoc. PR [537](https://github.com/tiangolo/fastapi/pull/537) by [Trim21](https://github.com/Trim21).
* Fix handling `4XX` responses overriding default `422` validation error responses. PR [517](https://github.com/tiangolo/fastapi/pull/517) by [tsouvarev](https://github.com/tsouvarev).
* Fix typo in documentation for [Simple HTTP Basic Auth](https://fastapi.tiangolo.com/tutorial/security/http-basic-auth/#simple-http-basic-auth). PR [514](https://github.com/tiangolo/fastapi/pull/514) by [prostomarkeloff](https://github.com/prostomarkeloff).
* Fix incorrect documentation example in [first steps](https://fastapi.tiangolo.com/tutorial/first-steps/). PR [#511](https://github.com/tiangolo/fastapi/pull/511) by [IgnatovFedor](https://github.com/IgnatovFedor).
* Add support for Swagger UI [initOauth](https://github.com/swagger-api/swagger-ui/blob/master/docs/usage/oauth2.md) settings with the parameter `swagger_ui_init_oauth`. PR [#499](https://github.com/tiangolo/fastapi/pull/499) by [zamiramir](https://github.com/zamiramir).