Allow to specify charset in @Produces/@Consumes using attributes

The standard should allow to set charset in an easier way than doing string concatenation

```
@Produces("application/json; charset=UTF-8")
```

Something like this in case of a single MediaType

```
@Produces(type = MediaType.APPLICATION_JSON_TYPE, charset = StandardCharsets.UTF-8)
```
#### Affected Versions
[2.0.1]