feat(Apollo): Format Schema For Apollo Gateway

[minhaj-shakeel]

Fixes GRAPHQL-951.
This PR modifies GraphQL generated schema in order to support federation.
It also removes some directive definitions which currently give validation error in apollo.
This PR also removes generated mutations and mutation input types from the Generated schema.

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This change is 

[pawanrawal]

Reviewable status: 0 of 10 files reviewed, 7 unresolved discussions (waiting on @minhaj-shakeel)

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graphql/admin/admin.go, line 390 at r1 (raw file):

func SchemaValidate(sch string) error {
	schHandler, err := schema.NewHandler(sch, true, false)

for Apollo also, this should be called once when schema updates and then be stored in memory

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graphql/e2e/schema/apolloServiceResponse.graphql, line 5 at r1 (raw file):

#######################

type Todo @key(fields: "id") {

Rename file to apollo_service_response.graphql

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graphql/schema/gqlschema.go, line 898 at r1 (raw file):

// completeSchema generates all the required types and fields for
// query/mutation/update for all the types mentioned in the schema.
// In case of Apollo service Query, input types from mutations and mutations

from queries and mutations

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graphql/schema/gqlschema.go, line 996 at r1 (raw file):

		}

		if apolloServiceQuery && hasExtends(defn) {

this can be moved above the params definition

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graphql/schema/gqlschema.go, line 2410 at r1 (raw file):

// var "apolloServiceQuery" is used to distinguish Schema String from what should be
// returned as a result of apollo service query. In case of Apollo service query, Schema
// misses some of the directive definitions which are currently not supported at the GateWay.

Schema removes some of the

gateway

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graphql/schema/schemagen.go, line 80 at r1 (raw file):

// some directives which are not exposed to the Apollo Gateway
// as they are failing in the schema validation which is a bug
// in their library.

Add link to GitHub issue on the Apollo project

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graphql/schema/schemagen.go, line 81 at r1 (raw file):

// as they are failing in the schema validation which is a bug
// in their library.
func (s *handler) GQLSchemaWithoutApolloExtras() string {

Add some unit tests for this also where given some input schemas and the output schema that we send to Apollo.