Serialize enum argument values in AddArgumentsAsVariables

[stefanprobst]

The AddArgumentsAsVariables transform currently takes the variable values directly from args. This PR serializes all GraphQLEnumType argument values before, so that the variable value contains the enum key, not the internal enum value. This avoids errors with merged schemas.

Not sure if the same thing should also be done with custom scalars(???) I left those alone since I got a bit confused there - the serialize/parseValue/parseLiteral methods don't seem to be carried over in schema merging (because keepResolvers will always be false in recreateType???)

EDIT (07/18): This has been merged into graphql-tools-fork with additional fixes for custom scalars by @yaacovCR - thanks!

[apollo-cla]

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[yaacovCR]

I think this fixes #1033.

[perrin4869]

Would be amazing to have this merged asap!

[kommander]

Any update on this?

[miguelocarvajal]

I tested this locally to stitch a couple of schemas, one with enum as arguments and it worked successfully.

What is needed to merge this?

[yaacovCR]

This is fixed in graphql-tools-fork v6.0.

[miguelocarvajal]

@yaacovCR Works like a charm! Thank you!

[bkstorm]

I hope this pull request will be merged asap. Without it, I can't use schema stitching.

[stefanprobst]

superseded by #1206