Release 2.6.1

[abernix]

This reverts an unintended breaking change in Apollo Server 2.6.1 which caused
typeDefs which were defined as a string rather than a DocumentNode (i.e.
wrapped in the gql template tagged literal) to result in an error within the
new isDirectiveDefined functionality.

This was reported in #2753.

TypeScript users would have been guarded against using typeDefs as a string,
but in JavaScript, there is no such protection and typeDefs historically have
frequently string-typed because of the internal graphql-tools usage which
supported this pattern.

And in case any readers of this didn't know, while many will wrap their
typeDefs in the gql tag hoping to gain syntax-highlighing in their editor
(a very good reason!), it does also do more — like parse its body into a
DocumentNode!

6adec0ad (Jesse Rosenberger, 9 minutes ago)
   Add CHANGELOG.md for breaking change inadvertently introduced in 2.6.0.

   Also added the MISSING `CHANGELOG.md` from the original release which I 
   somehow stomped out!

   Ref: #2428

c742335a (Jesse Rosenberger, 13 minutes ago)
   Revert "Avoid duplicate `cacheControl` directives via `isDirectiveDefined`
   (#2428)"

   This reverts commit 4e84defd23112ef19f502193105a7597bc6886be.

[abernix]

Successfully published:
 - apollo-cache-control@0.7.1
 - apollo-engine-reporting@1.2.1
 - @apollo/gateway@0.6.1
 - apollo-server-azure-functions@2.6.1
 - apollo-server-cloud-functions@2.6.1
 - apollo-server-cloudflare@2.6.1
 - apollo-server-core@2.6.1
 - apollo-server-express@2.6.1
 - apollo-server-fastify@2.6.1
 - apollo-server-hapi@2.6.1
 - apollo-server-koa@2.6.1
 - apollo-server-lambda@2.6.1
 - apollo-server-micro@2.6.1
 - apollo-server-plugin-base@0.5.1
 - apollo-server-plugin-response-cache@0.2.1
 - apollo-server-testing@2.6.1
 - apollo-server@2.6.1
 - apollo-tracing@0.7.1
 - graphql-extensions@0.7.1

[abernix]

Big thank you to @trevor-scheer for helping to track down the cause of this!

[wKovacs64]

Hmm, did the 2.6.1 release go sideways? Can't seem to install even though npm shows the 2.6.1 version exists. Tried a few of the packages listed (e.g. apollo-server@2.6.1, apollo-server-express@2.6.1, etc.). Yarn prompts to select a version and npm says the following:

npm ERR! code ETARGET
npm ERR! notarget No matching version found for apollo-server-express@2.6.1
npm ERR! notarget In most cases you or one of your dependencies are requesting
npm ERR! notarget a package version that doesn't exist.

[fullstackwebdev]

This broke my CICD server

yarn install v1.15.2
info No lockfile found.
[1/4] Resolving packages...
error Couldn't find any versions for "apollo-server-express" that matches "2.6.1"
info Visit https://yarnpkg.com/en/docs/cli/install for documentation about this command.

ERROR: for backend  (<Service: backend>, "The command '/bin/sh -c npx yarn' returned a non-zero code: 1")
Service 'backend' failed to build: The command '/bin/sh -c npx yarn' returned a non-zero code: 1
ERROR: Job failed: exit code 1

[trevor-scheer]

@wKovacs64 @fullstackwebdev can either of you still reproduce the issue? I was seeing it for a few minutes, but it seems to have cleared up for me. Seems like some funny CDN business.

[wKovacs64]

Agreed, seems fine now. Weird.