[Services] [FINAL COMMENT PERIOD] [RFC]: Defining a policy for REST API result format versioning / negotiation

Hi, we are considering a policy for REST API end point result format versioning and negotiation. The background and considerations are spelled out in a task and mw.org page: https://phabricator.wikimedia.org/T124365 https://www.mediawiki.org/wiki/Talk:API_versioning Based on the discussion so far, have come up with the following candidate solution: 1) Clearly advise clients to explicitly request the expected mime type with an Accept header. Support older mime types (with on-the-fly transformations) until usage has fallen below a very low percentage, with an explicit sunset announcement. 2) Always return the latest content type if no explicit Accept header was specified. We are interested in hearing your thoughts on this. Once we have reached rough consensus on the way forward, we intend to apply the newly minted policy to an evolution of the Parsoid HTML format, which will move the data-mw attribute to a separate metadata blob. Gabriel Wicke