* core: return response object from runHttpQuery
* core: change gqlResponse to graphqlResponse and add custom RequestInit type
* core: add cache-control headers based on the calcualted maxAge
* core: add extensions check during cache-control header creation
* core: create headers when cacheControl is not enabled otherwise pass through extensions
* express: initial tests of CDN cach-contol headers
* core: fixed tests with applyMiddleware and pass cacheControl config
* core: cache hint fixes, ignore when no maxAge, and check for rootKeys
* core: check for hints of length 0
* core: node 10 fails file upload test for some stream reason
* docs: add cdn caching section to features
* add space after // in comments
* fix feedback: proxy alignment and response creation
Adds cache-control toggles for http header calculation and stripping out
the cache control extensions from the respose.
Brings the default calculation of headers in line with the proxy.
* fix links in comments
* fix tests with null dereference
* update cdn docs and migration guide to include latest cdn configuration
* add not for engine migration to set engine to false
* add engine set to false in migration guide
* express: fixed tests
* address feedback to use omit and documentation
* docs: cdn caching is alternative to full response caching
* add back epipe check in upload tests
* feat: ApolloServer is created and exported by all variants
* docs: add initial docs around exporting ApolloServer
* feat: export gql from integrations
* docs: change apollo-server examples to use express with registerServer
* server: remove registerExpressServer
* core, docs: comment functions, fix api reference, context creation more like middleware args
* docs: fix integrationed typo
* apollo-server-core: add file upload hooks and configuration
* apollo-server-core: make requestOptions and fileUploadsConfig public fields in ApolloServerBase
* apollo-server-express: initial fileuploads middleware
* apollo-server-hapi: initial file uploads middleware
* core: remove fileuploads from constructor and add merge capabilities
* express: add fileuploads to registerServer and single test
* hapi: add fileuploads schema merge to registerServer
* express: add check for EPIPE and ignore it due to upload server issue
* core: add scalar Upload to server construction
