fix(types-json): Disable HTML escaping during JSON marshalling (#714)

Fixes #622

See docs about the default behavior of `json.Marshal`:
https://pkg.go.dev/encoding/json#Marshal
![image](https://user-images.githubusercontent.com/26760571/221586015-11f4f30b-0876-4a6f-8021-91ef4da94ffd.png)
See also https://pkg.go.dev/encoding/json#Encoder.SetEscapeHTML:
![image](https://user-images.githubusercontent.com/26760571/221586148-5f2c18b0-3ad7-46b4-a91b-1a56cfd6cfcd.png)


---

Author: erezrokah

schema/json.go

@@ -124,11 +124,16 @@ func (dst *JSON) Set(src any) error {
 		return &ValidationError{Type: TypeJSON, Msg: "use pointer to JSON instead of value", Value: value}
 
 	default:
-		buf, err := json.Marshal(value)
+		buffer := &bytes.Buffer{}
+		encoder := json.NewEncoder(buffer)
+		encoder.SetEscapeHTML(false)
+		err := encoder.Encode(value)
 		if err != nil {
 			return err
 		}
 
+		// JSON encoder adds a newline to the end of the output that we don't want.
+		buf := bytes.TrimSuffix(buffer.Bytes(), []byte("\n"))
 		// For map and slice jsons, it is easier for users to work with '[]' or '{}' instead of JSON's 'null'.
 		if bytes.Equal(buf, []byte(`null`)) {
 			if isEmptyStringMap(value) {

schema/json_test.go

@@ -43,6 +43,8 @@ func TestJSONSet(t *testing.T) {
 		{source: map[string]Foo{}, result: JSON{Bytes: []byte(`{}`), Status: Present}},
 
 		{source: nil, result: JSON{Status: Null}},
+
+		{source: map[string]any{"test1": "a&b", "test2": "😀"}, result: JSON{Bytes: []byte(`{"test1": "a&b", "test2": "😀"}`), Status: Present}},
 	}
 
 	for i, tt := range successfulTests {