Switch to Json.mapper() for JSON schema output in GetCollectionsSchemaImpl

[nls-jajuko]

io.swagger.v3.core.util.Json.mapper() might/would output conformant JSON Schema

[nls-jajuko]

something like this maybe

  import io.swagger.v3.core.util.Json;
//,,,
   ObjectMapper schemaMapper = Json.mapper();

//,,,

   ResponseBuilder builder = Response.ok();
        builder.type(MediaTypes.APPLICATION_SCHEMA);
        builder.entity(schemaMapper.writeValueAsString(definition));

        return builder.build();

[nls-jajuko]

seems to break /api without this annotation

    @ResponseClass(SchemaDefinition.class)

[jampukka]

seems to break /api without this annotation

    @ResponseClass(SchemaDefinition.class)

Yes, the /api functionality is a bit delicate.

[nls-jajuko]

OpenAPIObjectMapperProvider might/should solve this if registered with correct mime type for schema output.
@Produces(value = {MediaTypes.APPLICATION_SCHEMA,MediaTypes.APPLICATION_OPENAPI_V3})