Add "noomitempty" norman tag

Example usage:

  Labels map[string]string `json:"labels" norman:"noomitempty"`

Resulting API schema:
  "labels": {
    "create": true,
    "noOmitEmpty": true,
    "nullable": true,
    "type": "map[string]",
    "update": true
  }

Generated client code:

  Labels                         map[string]string                  `json:"labels" yaml:"labels"`

Without this, the field would normally have `,omitempty` as part of the
json and yaml tags.

generator/generator.go

@@ -30,8 +30,9 @@ var (
 )
 
 type fieldInfo struct {
-	Name string
-	Type string
+	Name        string
+	Type        string
+	NoOmitEmpty bool
 }
 
 func getGoType(field types.Field, schema *types.Schema, schemas *types.Schemas) string {
@@ -110,8 +111,9 @@ func getTypeMap(schema *types.Schema, schemas *types.Schemas) map[string]fieldIn
 			continue
 		}
 		result[field.CodeName] = fieldInfo{
-			Name: name,
-			Type: getGoType(field, schema, schemas),
+			Name:        name,
+			Type:        getGoType(field, schema, schemas),
+			NoOmitEmpty: field.NoOmitEmpty,
 		}
 	}
 	return result

generator/type_template.go

@@ -30,7 +30,7 @@ type {{.schema.CodeName}} struct {
     types.Resource
 {{- end}}
     {{- range $key, $value := .structFields}}
-        {{$key}} {{$value.Type}} %BACK%json:"{{$value.Name}},omitempty" yaml:"{{$value.Name}},omitempty"%BACK%
+        {{$key}} {{$value.Type}} %BACK%json:"{{$value.Name}}{{if not $value.NoOmitEmpty }},omitempty{{end}}" yaml:"{{$value.Name}}{{if not $value.NoOmitEmpty}},omitempty{{end}}"%BACK%
     {{- end}}
 }
 

types/reflection.go

@@ -393,6 +393,8 @@ func applyTag(structField *reflect.StructField, field *Field) error {
 			field.ValidChars = value
 		case "invalidChars":
 			field.InvalidChars = value
+		case "noomitempty":
+			field.NoOmitEmpty = true
 		default:
 			return fmt.Errorf("invalid tag %s on field %s", key, structField.Name)
 		}

types/types.go

@@ -150,6 +150,7 @@ type Field struct {
 	Description  string      `json:"description,omitempty"`
 	CodeName     string      `json:"-"`
 	DynamicField bool        `json:"dynamicField,omitempty"`
+	NoOmitEmpty  bool        `json:"noOmitEmpty,omitempty"`
 }
 
 type Action struct {