Update to Rack v2.1.4

This is needed to address a few outstanding CVEs and fix cookie timestamp formats.

Rack v2.1.x no longer coerces the body to a string. Previously in a few places the Grape API was returning the status code as an integer, which Grape used as the response body. To preserve the legacy behavior, we explicitly set the body to the stringified integer.

Full list of changes: https://github.com/rack/rack/compare/2.0.9..2.1.4

## [2.1.4] - 2020-06-15

- [CVE-2020-8184] When parsing cookies, only decode the value

## [2.1.3] - 2020-05-12

- [CVE-2020-8161] Use Dir.entries instead of Dir[glob] to prevent user-specified glob metacharacters
-
## [2.1.2] - 2020-01-27

- Fix multipart parser for some files to prevent denial of service ([@aiomaster](https://github.com/aiomaster))
- Fix `Rack::Builder#use` with keyword arguments ([@kamipo](https://github.com/kamipo))
- Skip deflating in Rack::Deflater if Content-Length is 0 ([@jeremyevans](https://github.com/jeremyevans))
- Remove `SessionHash#transform_keys`, no longer needed ([@pavel](https://github.com/pavel))
- Add to_hash to wrap Hash and Session classes ([@oleh-demyanyuk](https://github.com/oleh-demyanyuk))
- Handle case where session id key is requested but missing ([@jeremyevans](https://github.com/jeremyevans))

## [2.1.1] - 2020-01-12

- Remove `Rack::Chunked` from `Rack::Server` default middleware. ([#1475](https://github.com/rack/rack/pull/1475), [@ioquatix](https://github.com/ioquatix))

## [2.1.0] - 2020-01-10

### Added

- Add support for `SameSite=None` cookie value. ([@hennikul](https://github.com/hennikul))
- Add trailer headers. ([@eileencodes](https://github.com/eileencodes))
- Add MIME Types for video streaming. ([@styd](https://github.com/styd))
- Add MIME Type for WASM. ([@buildrtech](https://github.com/buildrtech))
- Add `Early Hints(103)` to status codes. ([@egtra](https://github.com/egtra))
- Add `Too Early(425)` to status codes. ([@y-yagi]((https://github.com/y-yagi)))
- Add `Bandwidth Limit Exceeded(509)` to status codes. ([@CJKinni](https://github.com/CJKinni))
- Add method for custom `ip_filter`. ([@svcastaneda](https://github.com/svcastaneda))
- Add boot-time profiling capabilities to `rackup`. ([@tenderlove](https://github.com/tenderlove))
- Add multi mapping support for `X-Accel-Mappings` header. ([@yoshuki](https://github.com/yoshuki))
- Add `sync: false` option to `Rack::Deflater`. (Eric Wong)
- Add `Builder#freeze_app` to freeze application and all middleware instances. ([@jeremyevans](https://github.com/jeremyevans))
- Add API to extract cookies from `Rack::MockResponse`. ([@petercline](https://github.com/petercline))

### Changed

- Don't propagate nil values from middleware. ([@ioquatix](https://github.com/ioquatix))
- Lazily initialize the response body and only buffer it if required. ([@ioquatix](https://github.com/ioquatix))
- Fix deflater zlib buffer errors on empty body part. ([@felixbuenemann](https://github.com/felixbuenemann))
- Set `X-Accel-Redirect` to percent-encoded path. ([@diskkid](https://github.com/diskkid))
- Remove unnecessary buffer growing when parsing multipart. ([@tainoe](https://github.com/tainoe))
- Expand the root path in `Rack::Static` upon initialization. ([@rosenfeld](https://github.com/rosenfeld))
- Make `ShowExceptions` work with binary data. ([@axyjo](https://github.com/axyjo))
- Use buffer string when parsing multipart requests. ([@janko-m](https://github.com/janko-m))
- Support optional UTF-8 Byte Order Mark (BOM) in config.ru. ([@mikegee](https://github.com/mikegee))
- Handle `X-Forwarded-For` with optional port. ([@dpritchett](https://github.com/dpritchett))
- Use `Time#httpdate` format for Expires, as proposed by RFC 7231. ([@nanaya](https://github.com/nanaya))
- Make `Utils.status_code` raise an error when the status symbol is invalid instead of `500`. ([@adambutler](https://github.com/adambutler))
- Rename `Request::SCHEME_WHITELIST` to `Request::ALLOWED_SCHEMES`.
- Make `Multipart::Parser.get_filename` accept files with `+` in their name. ([@lucaskanashiro](https://github.com/lucaskanashiro))
- Add Falcon to the default handler fallbacks. ([@ioquatix](https://github.com/ioquatix))
- Update codebase to avoid string mutations in preparation for `frozen_string_literals`. ([@pat](https://github.com/pat))
- Change `MockRequest#env_for` to rely on the input optionally responding to `#size` instead of `#length`. ([@janko](https://github.com/janko))
- Rename `Rack::File` -> `Rack::Files` and add deprecation notice. ([@postmodern](https://github.com/postmodern)).
- Prefer Base64 “strict encoding” for Base64 cookies. ([@ioquatix](https://github.com/ioquatix))

### Removed

- Remove `to_ary` from Response ([@tenderlove](https://github.com/tenderlove))
- Deprecate `Rack::Session::Memcache` in favor of `Rack::Session::Dalli` from dalli gem ([@fatkodima](https://github.com/fatkodima))

### Fixed

- Eliminate warnings for Ruby 2.7. ([@osamtimizer](https://github.com/osamtimizer]))

### Documentation

- Update broken example in `Session::Abstract::ID` documentation. ([tonytonyjan](https://github.com/tonytonyjan))
- Add Padrino to the list of frameworks implmenting Rack. ([@wikimatze](https://github.com/wikimatze))
- Remove Mongrel from the suggested server options in the help output. ([@tricknotes](https://github.com/tricknotes))
- Replace `HISTORY.md` and `NEWS.md` with `CHANGELOG.md`. ([@twitnithegirl](https://github.com/twitnithegirl))
- CHANGELOG updates. ([@drenmi](https://github.com/Drenmi), [@p8](https://github.com/p8))

Relates to:

• #36362 (closed)
• #228622 (closed)