support .gqlgen.yml

[vvakame]

refs #161
I'm implemented types.yaml support 👍

Now, We can processing 3 forms of types.* file.

old one.

{
    "Element": "github.com/vektah/gqlgen/test.Element"
}

JSON form.

{
    "Element": {
        "entityPath": "github.com/vektah/gqlgen/test.Element"
    }
}

YAML form.

- typeName:   Element
  entityPath: github.com/vektah/gqlgen/test.Element

If json is used it may be better to display an error to use yaml.

[vvakame]

👀 vvakame@26f865b

- typeName:   User
  entityPath: remote_api.User
  fields:
  - fieldName: likes
    resolver:  true

[vektah]

I appreciate the PR but I think this needs a bit more thought.

I was picturing something more like

models:
    User: 
        model: github.com/my/pkg/user.User
        fields:
            ID: 
                resolver: true

Because the unique element (typeName, fieldName) are keys, linters will fail on dupes.

Also if we head down this path I think we should just deprecate (and provide command to convert) the old format to the new.

It probably probably becomes a more general .gqlgen.yml and should probably support setting all the command line args.

[vektah]

Yaml is a superset of json, so you should be able to remove the json codepath here entirely.

This also means you can use yaml comments in json files and leave on trailing newlines I think.

[vvakame]

@vektah thank for advice!

I added support about .gqlgen.yml.

schema: schema.graphql
output: generated.go
modeloutput: models/generated.go

models:
  Element:
    model: github.com/vektah/gqlgen/test.Element
  Viewer:
    model: github.com/vektah/gqlgen/test.Viewer
  User:
    model: remote_api.User

and, user use -typemap commandline option.
They will get the warning message likes below.

$ go run ../main.go -out generated.go -typemap types.json -models models/generated.go
you should use .gqlgen.yml with below content.

schema: schema.graphql
models:
  Element:
    model: github.com/vektah/gqlgen/test.Element
  User:
    model: remote_api.User
  Viewer:
    model: github.com/vektah/gqlgen/test.Viewer
output: generated.go
modeloutput: models/generated.go