graphql: remove custom directive from internal schema

[abhimanyusinghgaur]

This PR removes custom directive from internal schema and stores it in a separate mapping. @custom was never exposed externally through introspection, as GraphQL spec doesn't specify a way to query directives for a field in introspection. Also, as getGQLSchema resolver in /admin will be protected with Guardian auth, getGQLSchema will still have the @custom directive in its outputs for both schema and generatedSchema.

This PR also updates schemaExtras to reflect the current definition for @custom.

Fixes #GRAPHQL-347

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[pawanrawal]

nice and simple change!

Reviewed 35 of 35 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @abhimanyusinghgaur, @manishrjain, and @MichaelJCompton)

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graphql/schema/gqlschema.go, line 84 at r1 (raw file):

	method: HTTPMethod!
	body: String
	graphql: String

Even though the definition was incorrect, schema validation didn't fail? Is it again because schema extras are added later after the actual validation?

[abhimanyusinghgaur]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @manishrjain, @MichaelJCompton, and @pawanrawal)

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graphql/schema/gqlschema.go, line 84 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

Even though the definition was incorrect, schema validation didn't fail? Is it again because schema extras are added later after the actual validation?

Yes

[MichaelJCompton]

...we can't have a test that shows that it's not in the output schema right? because you can't actually query for that in graphql schema introspection?

Reviewable status: 1 of 36 files reviewed, 2 unresolved discussions (waiting on @abhimanyusinghgaur, @manishrjain, @MichaelJCompton, and @pawanrawal)

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graphql/schema/gqlschema.go, line 84 at r1 (raw file):

Previously, abhimanyusinghgaur (Abhimanyu Singh Gaur) wrote…

Yes

I actually wonder is it because gqlparser doesn't check directive inputs properly, we've bumped into that before.

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graphql/schema/wrappers.go, line 205 at r2 (raw file):

	// something like field.Directives.ForName("custom"), which results in iterating over all the
	// directives of the field.
	customDirectives map[string]map[string]*ast.Directive

so it includes Query and Mutation?

[abhimanyusinghgaur]

Yes

Reviewable status: 1 of 36 files reviewed, 2 unresolved discussions (waiting on @manishrjain, @MichaelJCompton, and @pawanrawal)

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graphql/schema/wrappers.go, line 205 at r2 (raw file):

Previously, MichaelJCompton (Michael Compton) wrote…

so it includes Query and Mutation?

Yes