fix: fixed the error that the file could not be found after packing

application/src/main/java/org/thingsboard/server/service/mail/DefaultTbMailConfigTemplateService.java

@@ -32,7 +32,7 @@ public class DefaultTbMailConfigTemplateService implements TbMailConfigTemplateS
 
     @PostConstruct
     private void postConstruct() throws IOException {
-        mailConfigTemplates = JacksonUtil.toJsonNode(new ClassPathResource("/templates/mail_config_templates.json").getFile());
+        mailConfigTemplates = JacksonUtil.toJsonNode(new ClassPathResource("/templates/mail_config_templates.json").getInputStream());
     }
 
     @Override

common/util/src/main/java/org/thingsboard/common/util/JacksonUtil.java

@@ -35,6 +35,7 @@ import org.thingsboard.server.common.data.kv.KvEntry;
 
 import java.io.File;
 import java.io.IOException;
+import java.io.InputStream;
 import java.io.Reader;
 import java.io.Writer;
 import java.util.Arrays;
@@ -182,6 +183,15 @@ public class JacksonUtil {
         }
     }
 
+    public static JsonNode toJsonNode(InputStream value) {
+        try {
+            return value != null ? OBJECT_MAPPER.readTree(value) : null;
+        } catch (IOException e) {
+            throw new IllegalArgumentException("The given InputStream value: "
+                                               + value + " cannot be transformed to a JsonNode", e);
+        }
+    }
+
     public static ObjectNode newObjectNode() {
         return newObjectNode(OBJECT_MAPPER);
     }