Complete key info for 'Raven Metadata' service

The page already exists (under docs/services) in template form with braces indicating where details should be inserted. While the layout of each page should be kept as similar as possible, the information requested may not be appropriate or additional info may by useful. In this case, please document your reasoning in the MR. Similarly, It may make sense to merge/split key info pages depending on how you class services. Again, please document your reasoning in the MR.