Null As for graphql

[theishshah]

Addressing #62

I added the flag for --null-as and made some assumptions about how the implementation should work, however it should be trivial to switch that logic if you have a better/different idea in mind

[thomasdfischer]

The flag code looks good. To debug for this PR, workflow will be something like this:

$ schema infer --graphql
{
    "name": "Tom",
    "email": null
}^D
error: failed to serialize schema
cannot infer type of null value (see key 'email')

^ that demonstrates how schema works on master.

We want to be able to explicitly tell schema to use the type string/bool/number in place of null values in the generated graphql schema. When --null-as is implemented, users should be able to do this:

$ schema infer --graphql --null-as=string
{
    "name": "Tom",
    "email": null
}^D
type Object {
    name: String!
    email: String!
}

[theishshah]

I think there is an issue when building the schema map that is disjoint from the actual build schema stuff I changed, which is causing a basic test I wrote to fail, unsure of how best to go forward

[thomasdfischer]

schema infer --graphql works like this right now

1. Read incoming JSON/YAML/TOML, etc.
2. Create an jsonsch.Schema object in memory
3. Call the method js.ToGraphQLSchema() to convert it to a graphqlsch.Schema object
4. Serialize the graphqlsch.Schema object

All the logic of this PR looks correct, but it's in part 2 (from the numbering above^) of the codebase. Instead, part 3 should be modified. The lines we need to modify are here:

call to handlePrimitive: https://github.com/Confbase/schema/blob/master/jsonsch/jsonsch.go#L32

actual line that rejects null values in handlePrimitive: https://github.com/Confbase/schema/blob/master/jsonsch/jsonsch.go#L96

call to handleArraySchema: https://github.com/Confbase/schema/blob/master/jsonsch/jsonsch.go#L44

actual line that rejects null values: https://github.com/Confbase/schema/blob/master/jsonsch/jsonsch.go#L140

The codebase has zero documentation right now, so no question is a dumb question. Feel free to yell at me if anything is confusing

[thomasdfischer]

Test looks good except we don't need --omit-required=false since it has no bearing on graphql schemas. When that flag is true, the "required" field is omitted from JSON schemas.

[theishshah]

Alright, I think this should be good to merge 😄