feat: upgrade to graphql@15.0.0 for #1191

[acao]

Have graphql@15.0.0 working as a baseline, without necessarily adding support for new language features yet. Consequently, it requires an upgrade to graphql-config-rc.2. This is why we are still in alpha! Further PRs will follow that address things like interfaces implementing interfaces, etc

• use instrospectionQuery() rather than constant (deprecated)
• bump resolutions for 15
• minor validation error formating issues
• ensure GraphiQL works end to end (view deploy preview, cypress suite)
• issue with graphql-config and server tests? potentially graphql-config is not working with 15.
• check server for regressions, use with a vscode extension
• manually check for more specific regressions in GraphiQL, other LSP implementations that are related to breaking changes.

[acao]

@Urigo so we are using graphql-config@2.2.1 still, and it seems theres a bug with the introspection result in this test:

https://github.com/graphql/graphiql/blob/chore/graphql-15-rc/packages/graphql-language-service-server/src/__tests__/GraphQLCache-test.js#L46

when i print out the result of the introspection request, i get:
Error: Must provide Source. Received: undefined.

[acao]

only bug left is that this type is deprecated in graphql 15 (though we can work around this):

@ardatan @Urigo

maybe i can open an issue?

[acao]

ardatan/graphql-tools#1 i think this is the right place?

[Urigo]

I think this was already fixed on graphql-toolkit's master.

tomorrow we'll make sure to have updated versions of it published

[acao]

@Urigo everything looks good now, thank you!

[codecov]

Codecov Report

Merging #1204 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1204   +/-   ##
=======================================
  Coverage   58.98%   58.98%           
=======================================
  Files          60       60           
  Lines        3023     3023           
  Branches      806      806           
=======================================
  Hits         1783     1783           
  Misses       1194     1194           
  Partials       46       46           

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[acao]

@IvanGoncharov it's finally ready for you to review, what do you think?

[acao]

@IvanGoncharov I think the only thing we missed here as a baseline is removing the peer dependencies on lower versions of graphql. We should only support 14 and 15 now correct?