Fixes drupal-graphql#601: Treat invalid payloads as empty payloads.

Added missing language url context to menu links.

Contextual language handling. (drupal-graphql#550)

* Intermediate commit, not functional.

* Don't abort context retrieval on falsy path elements.

* Removed all implicit language contexts.

* Contextual language negotiation.

* Enforcing graphql language negotiation through config overrides.

* Fixing language negotiator.

* Fixed negotiation.

* Ignore language cache contexts.

* Added upgrade instructions for languages.

* Docs fix.

* Fix to also work without language module enabled.

* Fixed wrong return, has to be yield.

* Added core 8.5 tests.

* Docs fix.

* Moved contextual language to service.

* Travis debug.

* Removed travis debug.

* Renamed test class according to file.

* More tests and resulting fixes.

* Simplified language context.

* Explicit callable execution.

* More fine grained tests.

* Test negotiator initialization result.

* Test cleanup.

* Test disable negotiator fix.

* Debugging ...

* Debugging ...

* Debugging ...

* Debugging ...

* Check negotiator instance.

* Changed module initialization order.

* Depending on language module.

* Revert "Depending on language module."

This reverts commit f8df099

* Revert "Changed module initialization order."

This reverts commit bbaa77f

* Proper service provider classname.

* Properly injecting the language context.

* Annotation style fixes.

* Revert "Properly injecting the language context."

This reverts commit c358b53

* Real setter injection.

* Moved property to top.

* Use language cache contexts to conditionally set the graphql language context.

* Enabled multilingual features for all tests to catch potential context leaks.

* Ignore language contexts when creating the cache key.

* Reproducing leaking translation context.

* Add language_content cache context to RouteEntity since the access
handler emits it for some reason.

* Fixed exception expectation.

Fixing filter conjunction.

Test framework. (drupal-graphql#489)

Allow posting query and variables to GraphiQL.

Allow less specific query providers e.g. to enable automated persiste… (

drupal-graphql#448)

Tagging beta release.

Refactoring schema builder logic. (drupal-graphql#404)

Moving graphql_xml, graphql_json and graphql_twig into their own modu…

…les. (drupal-graphql#393)