Document Authorization/Anvil processes

[aiboyles]

• Determine how Anvil fits into the current ecosystem.
• Document Anvil's role and processes as they currently stand.
• Document how Anvil integrates with Xenia.
• Add Anvil/Authorization to the Architectural Overview diagram.

[aiboyles]

Backlogging this, since Anvil is not currently really integrated into Coral. Revisit once this gets a bit further along.

[kgardnr]

This is a WIP, closing