Implement additional formats from previous version of API (pds4+xml, pds4+json)

[jordanpadams]

💡 Description

Need to add back pds4+json and pds4+xml response formats back into the API.

Sub-tasks

• As a user, I want to receive a XML response that contains the PDS4 label metadata in XML format (application/vnd.nasa.pds.pds4+xml)  #440
• As a user, I want to receive a JSON response that contains the PDS4 label metadata in JSON format (application/vnd.nasa.pds.pds4+json) #450