fix(graphql): generate valid GraphQL for empty enums

[Garv978]

Summary

Fixes #248.

Generated GraphQL SDL could be invalid when processing Concerto models.

Changes

• Generate a valid placeholder enum value for empty enums.
• Generate GraphQL scalar declarations for Concerto scalar declarations.
• Map Concept to the GraphQL JSON scalar.
• Use GraphQL type conversion consistently for map key/value types.
• Remove the GraphQL verification skips now that the generated SDL passes buildSchema.
• Update the GraphQL snapshots.

Verification

• npm test
• npx mocha test/codegen/codegen.js
• npx mocha test/verification
• Direct graphql.parse() validation
• Direct graphql.buildSchema() validation for hr_base.cto + hr.cto

All relevant GraphQL tests pass.

[apoorv7g]

Please add some more documentation, Looks good to me, I have tested this and it works. Thank you for your contribution @Garv978

@mttrbrts Can you have a look later, approving from my end.

[mttrbrts]

Can you explain this change? Concept should generated as the named types. This function is typically used just for scalar / primitive types.

[apoorv7g]

Please remove unused var and trailing spaces @Garv978 Always use npm run test and not just npm run test:verify as the former contains the test suite for the whole repo

[Garv978]

its festival time so i am busy give me a day or two please