Buy It Now + Starting price

[Nokhal]

Diamond cut ready (Update OR as new diamond)

Starting price where you prepay the marketplace fees (ie : you only lose money as a seller if there is no bid, no direct impact on final earnings)
Buy it now, giving buyer to instantly settle an auction and win an item if they pay for the asked price.
Ability for the seller to lower the buy it now price or cancel it, but not increase it
New events to easily track those new features from an Indexer (eg: Subgraph)

The code is

Diamond-cut ready, assuming an existing deployment. See comments in the GBMFacetExtensionOne.sol to know what to updated/add
Can also be deployed 'as is' to a completely new diamond
Untested within your UI/UX but have minimized the amount of new functions
fully retro-compatible with any existing flow and API if updating an existing diamond