Named queries without variables support

[ghost]

Added support for queries with empty named queries

query works() {
  q(func: has(name)) {
    name
  }
}

Fixes #3994

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This looks satisfactory for #3994

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Reviewed with ❤️ by PullRequest

[manishrjain]

@mangalaman93 : Please approve using the reviewable interface. Otherwise, it is hard to know that you indeed reviewed it.

Got a comment about adding another test. Add that and merge.

Reviewed 2 of 2 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @harshil-goel)

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gql/parser_test.go, line 57 at r1 (raw file):

func TestParseQueryNamedQuery(t *testing.T) {
	query := `
query works() {

Add another test for when works doesn't have round brackets.

query works { ... }