Update new data source page

Why is this change being made?

On some of the new data source request that came in in the past, we saw that using (complex) JSON data is not always straightforward. Formalizing with this MR that a Data Engineer can support or can take over flattening the data to a tabular format, from where it can be picked up by other GitLab Team members to model it towards PROD.

Author Checklist

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
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