ENG-22892 fix: UnmarshalRawMessage of a gql quoted string (#153)

(Fix idea suggested by @jarrodb)

Bug with this GQL schema: `json: JSON!`
and with the input `json: "json quotes strings"`

Output is wrong: `json.RawMessage("json quotes strings")`
For example this always fails:

```
var res any
json.Unmarshal(json.RawMessage("json quotes strings"), &res)
// invalid character 'j' looking for beginning of value
```

Correcting to:   `json.RawMessage("\"json quotes strings\"")`

---------

Signed-off-by: Jakub Bielecki <47531708+jabielecki@users.noreply.github.com>

entx/json.go

@@ -32,8 +32,6 @@ func MarshalRawMessage(t json.RawMessage) graphql.Marshaler {
 // UnmarshalRawMessage provides a graphql.Unmarshaler for json.RawMessage
 func UnmarshalRawMessage(v interface{}) (json.RawMessage, error) {
 	switch j := v.(type) {
-	case string:
-		return UnmarshalRawMessage([]byte(j))
 	case []byte:
 		return json.RawMessage(j), nil
 	case map[string]interface{}:

entx/json_test.go

@@ -0,0 +1,60 @@
+// Copyright 2023 The Infratographer Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package entx
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func TestUnmarshalRawMessage(t *testing.T) {
+	tests := []struct {
+		name    string
+		arg     interface{}
+		want    json.RawMessage
+		wantErr bool
+	}{{
+		name: "map",
+		arg:  map[string]any{"a": true},
+		want: json.RawMessage(`{"a":true}`),
+	}, {
+		name: "array",
+		arg:  []int{1, 2},
+		want: json.RawMessage(`[1,2]`),
+	}, {
+		name: "bytes",
+		arg:  []byte{'"', 'a', '"'},
+		want: json.RawMessage(`"a"`),
+	}, {
+		// In practice, this is the way graphql Unmarshal is processing input like {json: "a"}:
+		name: "string",
+		arg:  "a",
+		want: json.RawMessage(`"a"`),
+	}}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := UnmarshalRawMessage(tt.arg)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("UnmarshalRawMessage() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if !reflect.DeepEqual(got, tt.want) {
+				t.Errorf("UnmarshalRawMessage() = %s, want %s", got, tt.want)
+			}
+		})
+	}
+}