Adds support for flags enum

[PascalSenn]

Adds support for flag enums

Given the following enum

[Flags]
public enum Example { First, Second, Third }

public class Query { public Example Loopback(Example input) => input;

The following schema is produced

type Query {
    loopback(input: ExampleFlagsInput!): ExampleFlags
}

type ExampleFlags {
    isFirst: Boolean!
    isSecond: Boolean!
    isThird: Boolean!
}

input ExampleFlagsInput {
    isFirst: Boolean
    isSecond: Boolean
    isThird: Boolean
}

closes #1020

[spqr911]

Adds support for flag enums

Given the following enum

[Flags]
public enum Example { First, Second, Third }

public class Query { public Example Loopback(Example input) => input;

The following schema is produced

type Query {
    loopback(input: ExampleFlagsInput!): ExampleFlags
}

type ExampleFlags {
    isFirst: Boolean!
    isSecond: Boolean!
    isThird: Boolean!
}

input ExampleFlagsInput {
    isFirst: Boolean
    isSecond: Boolean
    isThird: Boolean
}

closes #1020

Flags still doesn'twork please reopen this issue.