Rest API error Content-Type when requesting resource content

**Describe the bug**
In rest documentation refers that when requesting a deployment's resource content the response content-type will be the same as the type returned in the resources 'mimeType' property but it is always text/html so its not possible to view a process diagram png

**Expected behavior**
Content-type in response header must be image/png for example when requesting a process diagram

**Additional context**
Flowable 6.5.0, Spring boot 2.2.6