Support of const keyword

[frankie-p]

I'm not a Json schema deep diver, but somehow I miss support for the const keyword (at least for C# code generation):

{
"title": "Person",
"type": "object",
"properties": {
"cmdType": {
"$comment": "This results in a string template literal when generating TS",
"const": "person"
},
...
}

[RicoSuter]

Ref: http://json-schema.org/understanding-json-schema/reference/generic.html#constant-values

[htbmw]

I noticed that the json schema validation for the const keyword has no effect.
If you convert the const to an enum with a single value, then validation works as expected.

See:
https://ajv.js.org/json-schema.html#const

[shuebner]

@htbmw
I use ajv to test a schema against known valid and invalid JSONs.
The schema has const in it and ajv does fail validation of a JSON that has another value than the one defined with const, as it should.

[dthomas-inspire]

Please also support the const keyword in the code generation. Per the const documentation, I'm using the following in a schema:

    "commandCode": {
      "const": 1319
    },

This produces the following C# code: public object CommandCode { get; set; }

I would really like the C# code to return the constant value.