Add metadata fields present in the JSON response to the XML response

[DavisRayM]

Changes / Features implemented

• Add non-list metadata fields to the XML attributes
• Update test to ensure the attributes are present

Steps taken to verify this change does what is intended

Included tests

Side effects of implementing this change

N/A

Before submitting this PR for review, please make sure you have:

• Included tests
• Updated documentation

API Response Change

This PR makes changes to the API Responses expected on the data endpoint /api/v1/data/<id>.xml. The following is the new structure suggested in this PR:

<submission-batch>
  <submission-item submissionData="" dateCreated="" formVersion="" objectID="" ...>
    <data/>
    <linked-resources>
       <notes/>
       <tags/>
       <attachments />
     <linked-resources/>
   <submission-item/>
<submission-batch/>

Why the server-meta -> linked-resources change ? It made more sense to name the node linked-resources since it predominantly includes resources linked to the submission rather than metadata for the submission.

Closes #2107